NCRACK(1) Ncrack Reference Guide NCRACK(1)NAMEncrack - Network authentication cracking tool
SYNOPSISncrack [Options] {target specification}
DESCRIPTION
Ncrack is an open source tool for network authentication cracking. It
was designed for high-speed parallel cracking using a dynamic engine
that can adapt to different network situations. Ncrack can also be
extensively fine-tuned for special cases, though the default parameters
are generic enough to cover almost every situation. It is built on a
modular architecture that allows for easy extension to support
additional protocols. Ncrack is designed for companies and security
professionals to audit large networks for default or weak passwords in
a rapid and reliable way. It can also be used to conduct fairly
sophisticated and intensive brute force attacks against individual
services.
Warning
Ncrack is a project started in the Summer of 2009. While it is
already useful for some purposes, it is still unfinished, beta
quality software. You can help out by testing it and reporting any
problems as described in the section called “BUGS”.
The output from Ncrack is a list of found credentials, if any, for each
of the targets specified. Ncrack can also print an interactive status
report of progress so far and possibly additional debugging information
that can help track problems, if the user selected that option.
A typical Ncrack scan is shown in Example 1. The only Ncrack arguments
used in this example are the two target IP addresses along with the the
corresponding ports for each of them. The two example ports 21 and 22
are automatically resolved to the default services listening on them:
ftp and ssh.
Example 1. A representative Ncrack scan
$ ncrack 10.0.0.130:21 192.168.1.2:22
Starting Ncrack 0.5 ( http://ncrack.org ) at 2016-01-03 22:10 EEST
Discovered credentials for ftp on 10.0.0.130 21/tcp:
10.0.0.130 21/tcp ftp: admin hello1
Discovered credentials for ssh on 192.168.1.2 22/tcp:
192.168.1.2 22/tcp ssh: guest 12345
192.168.1.2 22/tcp ssh: admin money$
Ncrack done: 2 services scanned in 156.03 seconds.
Ncrack finished.
The latest version of Ncrack can be obtained from
http://nmap.org/ncrack. The latest version of this man page is
available at http://nmap.org/ncrack/man.html .
OPTIONS SUMMARY
This options summary is printed when Ncrack is run with no arguments.
It helps people remember the most common options, but is no substitute
for the in-depth documentation in the rest of this manual.
Ncrack 0.5 ( http://ncrack.org )
Usage: ncrack [Options] {target and service specification}
TARGET SPECIFICATION:
Can pass hostnames, IP addresses, networks, etc.
Ex: scanme.nmap.org, microsoft.com/24, 192.168.0.1; 10.0.0-255.1-254
-iX <inputfilename>: Input from Nmap´s -oX XML output format
-iN <inputfilename>: Input from Nmap´s -oN Normal output format
-iL <inputfilename>: Input from list of hosts/networks
--exclude <host1[,host2][,host3],...>: Exclude hosts/networks
--excludefile <exclude_file>: Exclude list from file
SERVICE SPECIFICATION:
Can pass target specific services in <service>://target (standard) notation or
using -p which will be applied to all hosts in non-standard notation.
Service arguments can be specified to be host-specific, type of service-specific
(-m) or global (-g). Ex: ssh://10.0.0.10,at=10,cl=30 -m ssh:at=50 -g cd=3000
Ex2: ncrack-p ssh,ftp:3500,25 10.0.0.10 scanme.nmap.org google.com:80,ssl
-p <service-list>: services will be applied to all non-standard notation hosts
-m <service>:<options>: options will be applied to all services of this type
-g <options>: options will be applied to every service globally
Misc options:
ssl: enable SSL over this service
path <name>: used in modules like HTTP (´=´ needs escaping if used)
TIMING AND PERFORMANCE:
Options which take <time> are in seconds, unless you append ´ms´
(milliseconds), ´m´ (minutes), or ´h´ (hours) to the value (e.g. 30m).
Service-specific options:
cl (min connection limit): minimum number of concurrent parallel connections
CL (max connection limit): maximum number of concurrent parallel connections
at (authentication tries): authentication attempts per connection
cd (connection delay): delay <time> between each connection initiation
cr (connection retries): caps number of service connection attempts
to (time-out): maximum cracking <time> for service, regardless of success so far
-T<0-5>: Set timing template (higher is faster)
--connection-limit <number>: threshold for total concurrent connections
AUTHENTICATION:
-U <filename>: username file
-P <filename>: password file
--user <username_list>: comma-separated username list
--pass <password_list>: comma-separated password list
--passwords-first: Iterate password list for each username. Default is opposite.
--pairwise: Choose usernames and passwords in pairs.
OUTPUT:
-oN/-oX <file>: Output scan in normal and XML format, respectively, to the given filename.
-oA <basename>: Output in the two major formats at once
-v: Increase verbosity level (use twice or more for greater effect)
-d[level]: Set or increase debugging level (Up to 10 is meaningful)
--nsock-trace <level>: Set nsock trace level (Valid range: 0 - 10)
--log-errors: Log errors/warnings to the normal-format output file
--append-output: Append to rather than clobber specified output files
MISC:
--resume <file>: Continue previously saved session
--save <file>: Save restoration file with specific filename
-f: quit cracking service after one found credential
-6: Enable IPv6 cracking
-sL or --list: only list hosts and services
--datadir <dirname>: Specify custom Ncrack data file location
--proxy <type://proxy:port>: Make connections via socks4, 4a, http.
-V: Print version number
-h: Print this help summary page.
MODULES:
FTP, SSH, Telnet, HTTP(S), POP3(S), SMB, RDP, VNC, SIP, Redis, PostgreSQL, MySQL
EXAMPLES:
ncrack-v --user root localhost:22
ncrack-v -T5 https://192.168.0.1
ncrack-v -iX ~/nmap.xml -g CL=5,to=1h
SEE THE MAN PAGE (http://nmap.org/ncrack/man.html) FOR MORE OPTIONS AND EXAMPLES
TARGET SPECIFICATION
Everything on the Ncrack command-line that isn´t an option (or an
option argument) is treated as a target host specification. The
simplest case is to specify a target IP address or a hostname. Note,
that you also need to specify a service to crack for the selected
targets. Ncrack is very flexible in host/service specification. While
hostnames and IP addresses can be defined with the flexibility that you
are probably used to from Nmap, services along with service-specific
options have a unique specification style that enables a combination of
features to be taken advantage of.
Sometimes you wish to crack a whole network of adjacent hosts. For
this, Ncrack supports CIDR-style addressing. You can append /numbits to
an IPv4 address or hostname and Ncrack will try to crack every IP
address for which the first numbits are the same as for the reference
IP or hostname given. For example, 192.168.10.0/24 would send probes to
the 256 hosts between 192.168.10.0 11000000 10101000 00001010 00000000)
and 192.168.10.255 (binary: 11000000 10101000 00001010 11111111),
inclusive. 192.168.10.40/24 would crack exactly the same targets. Given
that the host scanme.nmap.org is at the IP address 64.13.134.52, the
specification scanme.nmap.org/16 would send probes to the 65,536 IP
addresses between 64.13.0.0 and 64.13.255.255. The smallest allowed
value is /0, which targets the whole Internet. The largest value is
/32, which targets just the named host or IP address because all
address bits are fixed.
CIDR notation is short but not always flexible enough. For example, you
might want to send probes to 192.168.0.0/16 but skip any IPs ending
with .0 or .255 because they may be used as subnet network and
broadcast addresses. Ncrack supports this through octet range
addressing. Rather than specify a normal IP address, you can specify a
comma-separated list of numbers or ranges for each octet. For example,
192.168.0-255.1-254 will skip all addresses in the range that end in .0
or .255, and 192.168.3-5,7.1 will target the four addresses
192.168.3.1, 192.168.4.1, 192.168.5.1, and 192.168.7.1. Either side of
a range may be omitted; the default values are 0 on the left and 255 on
the right. Using - by itself is the same as 0-255, but remember to use
0- in the first octet so the target specification doesn´t look like a
command-line option. Ranges need not be limited to the final octets:
the specifier will send probes to all IP addresses on the Internet
ending in 13.37 This sort of broad sampling can be useful for Internet
surveys and research.
Ncrack accepts multiple host specifications on the command line, and
they don´t need to be the same type. The command ncrack scanme.nmap.org
192.168.0.0/8 10.0.0,1,3-7.- -p22 does what you would expect.
While targets are usually specified on the command lines, the following
options are also available to control target selection:
-iX inputfilename (Input from Nmap´s -oX XML output format) .
Reads target/service specifications from an Nmap XML output file.
The Nmap XML file is created by scanning any hosts and specifying
the Nmap -oX option. Ncrack will automatically parse the IP
addresses and the corresponding ports and services that are open
and will use these targets for authentication auditing. This is a
really useful option, since it lets you essentially combine these
two tools -Nmap and Ncrack- for cracking only those services that
are surely open. In addition, if version detection has been enabled
in Nmap (-sV option), Ncrack will use those findings to recognize
and crack those services that are supported but are listening on
non-default ports. For example, if a host is having a server
listening on port 41414 and Nmap has identified that it is a SSH
service, Ncrack will use that information to crack it using the SSH
module. Of course, Ncrack is going to ignore open ports/services
that are not supported for authentication cracking by its modules.
-iN inputfilename (Input from Nmap´s -oN Normal output format) .
Reads target/service specifications from an Nmap Normal output
file. The Nmap Normal file is created by scanning any hosts and
specifying the Nmap -oN option. This works exactly like Ncrack´s
-iX option, the only difference being the format of the input file.
-iL inputfilename (Input from list) .
Reads target specifications from inputfilename. Passing a huge list
of hosts is often awkward on the command line, yet it is a common
desire. For example, you might want to crack a list of very
specific servers that have been specified for penetration testing.
Simply generate the list of hosts to crack and pass that filename
to Ncrack as an argument to the -iL option. Entries can be in any
of the formats accepted by Ncrack on the command line (IP address,
hostname, CIDR, octet ranges or Ncrack´s special host-service
syntax. Each entry must be separated by one or more spaces, tabs,
or newlines. You can specify a hyphen (-) as the filename if you
want Ncrack to read hosts from standard input rather than an actual
file. Note, however, that if hosts are specified without any
service, you will have to also provide services/ports for the
targets using the -p option.
--exclude host1[, host2[, ...]] (Exclude hosts/networks) .
Specifies a comma-separated list of targets to be excluded from the
scan even if they are part of the overall network range you
specify. The list you pass in uses normal Ncrack syntax, so it can
include hostnames, CIDR netblocks, octet ranges, etc. This can be
useful when the network you wish to scan includes untouchable
mission-critical servers, systems that are known to react adversely
to heavy load, or subnets administered by other people.
--excludefile exclude_file (Exclude list from file) .
This offers the same functionality as the --exclude option, except
that the excluded targets are provided in a newline, space, or tab
delimited exclude_file rather than on the command line.
SERVICE SPECIFICATION
No cracking session can be carried out without targeting a certain
service to attack. Service specification is one of the most flexible
subsystems of Ncrack and collaborates with target-specification in a
way that allows different option combinations to be applied. For Ncrack
to start running, you will have to specify at least one target host and
one associated service to attack. Ncrack provides ways to specify a
service by its default port number, by its name (as extracted from the
ncrack-services file) or both. Normally, you need to define both name
and port number only in the special case where you know that a
particular service is listening on a non-default port.
Ncrack offers two distinct ways with which services will be applied to
your targets: per-host service specification and global specification.
Per-host service specification
Services specified in this mode are written next to the host and
apply to it only. Keep in mind, however, that target-specification
allows wildcards/netmasks, which essentially means that applying a
per-host service specification format to that particular target
will affect all of the expanded ones as a result. The general
format is:
[service-name]://target:[port-number]
where target is a hostname or IP address in any of the formats
described in the target-specification section, [service-name] is
one of the common service names as defined in the ncrack-services
file (e.g ssh, http) and [port-number] is what it obviously means.
Ncrack can determine the default port numbers for each of the
services it supports, as well as being able to deduce the service
name when a default port number has been specified. Specifying both
has meaning only when the user has a priori knowledge of a service
listening on a non-default port number. This can easily be
determined by using version detection like the one offered by
Nmap´s -sV option.
Example 2. Per-host service specification example
$ ncrack scanme.nmap.org:22 ftp://10.0.0.10 ssh://192.168.1.*:5910
The above command will try to crack hosts: scanme.nmap.org on SSH
service (default port 22), 10.0.0.10 on FTP service (default port
21) and 192.168.1.0 - 192.168.1.255 (all of this C subnet) on SSH
service on non-default port 5910 which has been explicitly
specified. In the last case, Ncrack wouldn´t be able to determine
that the subnet hosts are to be scanned against the SSH service on
that particular port without the user explicitly asking for it,
because there isn´t any mapping of port-number 5910 to service SSH.
Global service specification
Services specified in this mode are applied to all hosts that
haven´t been associated with the per-host service specification
format. This is done using the -p option. While this facility may
be similar to that of Nmap´s, you should try not to confuse it,
since the functionality is of a slightly different nature. Services
can be specified using comma separated directives of the general
format:
-p [service1]:[port-number1],[service2]:[port-number2],...
As usual, you need not specify both service name and port number
since Ncrack knows the mappings of default-services to default-port
numbers. Be careful though not to include any space between each
service-name and/or port number, because Ncrack will think that the
argument after the space is a host as per the rule "everything that
isn´t an option is a target specification".
Example 3. Global service specification example
$ ncrack scanme.nmap.org 10.0.0.120-122 192.168.2.0/24 -p 22,ftp:3210,telnet
The above command will try to crack all of the specified hosts
scanme.nmap.org, 10.0.0.120, 10.0.0.121, 10.0.0.122 and the C class
subnet of 192.168.2.0 against the following services: SSH service
(mapped from default port 22), FTP service on non-default port
3210, and TELNET service on default port 23.
Of course, Ncrack allows you to combine both modes of service
specification if you deem that as necessary. Normally, you will only
need to specify a couple of services but cracking a lot of hosts
against many different services might be a longterm project for large
networks that need to be consistently audited for weak passwords. If
you are in doubt, about which hosts and services are going to be
cracked with the current command, you can use the -sL option (see below
for explanation).
SERVICE OPTIONS
Apart from general service specification, Ncrack allows you to provide
a multitude of options that apply to each or a subset of your targets.
Options include timing and performance optimizations (which are
thoroughly analyzed in a separate section), SSL enabling/disabling and
other module-specific parameters like the relative URL path for the
HTTP module. Options can be defined in a variety of ways which include:
per-host options, per-module options and global options. Since a
combination of these options may be used, there is a strict hierarchy
of precedence which will be discussed later.
Per-host Options
Options in this mode apply only to the host(s) they are referring
to and are written next to it according to the following format:
[service-name]://target:[port-number],opt1=optval1,opt2=optval,...
The format concerning the service specification which comes before
the options, has been explained in the previous section. optN is
referring to any of the option names that are available (a list
will follow below), while optvalN determines the value of that
option and depends on the nature of it. For example, most
timing-related options expect to receive numbers as values, while
the path option obviously needs a string argument.
Per-module Options
Options in this mode apply to all hosts that are associated with
the particular service/module. This is accomplished using the -m
which is defined with the format:
-m service-name:opt1=optval1,opt2=optval2,...
This option can be invoked multiple times, for as many different
services as you might need to define service-wide applicable
options. Each iteration of this option must refer to only one
service. However, to avoid confusion, this option had better not be
called more than one time for the same service, although this is
allowed and the last iteration will take precedence over the
previous ones for all redefined option values.
Global Options
Options in this mode apply to all hosts regardless of which service
they are associated with. This is accomplished using the -g as
follows:
-g opt1=optval1,opt2=optval2,...
This acts as a convenience option, where you can apply options to
all services globally. Everything else regarding the available
options and option values is the same as the previous modes.
List of available Service Options
Below follows a list of all the currently available service options.
You can apply them with any of the three modes described above. The
last six of the options are timing related and will be analyzed in
Section "Timing and Performance" of this manual.
ssl: enable SSL over this service
path: path-name used in modules like HTTP (´=´ needs escaping if used)
cl (min connection limit): minimum number of concurrent parallel connections
CL (max connection limit): maximum number of concurrent parallel connections
at (authentication tries): authentication attempts per connection
cd (connection delay): delay time between each connection initiation
cr (connection retries): caps number of service connection attempts
to (time-out): maximum cracking time for service, regardless of success so far
ssl (Enable/Disable SSL over service)
By enabling SSL, Ncrack will try to open a TCP connection and then
negotiate a SSL session with the target. Everything will then be
transparently encrypted and decrypted. However, since Ncrack´s job
is to provide speed rather than strong crypto, the algorithms and
ciphers for SSL are chosen on an efficiency basis. Possible values
for this option are ´yes´ but just specifying ssl would be enough.
Thus, this is the only option that doesn´t need to be written in
the opt=optval format. By default, SSL is disabled for all services
except those that are stricly dependent on it like HTTPS.
path <name> (Path name for relative URLs)
Some services like HTTP or SVN usually require a specific path in
the URL. This option takes that pathname string as its value. The
path is always relative to the hostname or IP address, so if you
want to target something like http://foobar.com/login.php the path
must take the value path=login.php . The initial ´/´ is added if
you omit it. However, it is usually better if you explicitly
specify it at the end of pathnames that are directories. For
example, to crack the directory for
http://foobar.com/protected-dir/ , it would be better if you wrote
it as path=protected-dir/ . This is to avoid the (very) slight
probability of a false positive, because there are cases where Web
servers might reply with a "301 Moved Permanently" for a
non-successful attempt. They normally send that reply, when a
successful attempt is made for a requested password-protected path
which has omitted the ending ´/´ but the requested source is
actually a directory. Consequently, Ncrack regards that reply as
having succeeded in the authentication attempt.
Also be careful with the symbol ´=´, since it is used by Ncrack for
argument parsing and you will have to espace it if it is included
in the URL.
By default, the path-name is initialized to ´/´, but will be
ignored by services that do not require it.
Service Option Hierarchy
As already noted, Ncrack allows a combination of the three different
modes of service option specification. In that case, there is a strict
hierarchy that resolves the order in which conflicting values for these
options take precedence over each other. The order is as follows,
leftmost being the highest priority and rightmost the lowest one:
Per-host options > Per-module options > Global options >
Timing-Template (for timing options only)
The concept of the "Timing-Template" will be explained in the Section
"Timing and Performance", but for now, just have in mind that its
values have the least prevalence over everything else and essentially
act as defaults for everything timing-related. Global options specified
with -g have the directly higher precedence, while -m per-module
options are immediately higher. In the top of the hierarcy reside the
per-host options which are essentially the most specific ones.
Consequently, you can see that the pattern is: the more specific the
higher the precedence.
Example 4. Service Option Hierarchy example
$ ncrack scanme.nmap.org:22,cl=10,at=1 10.0.0.120 10.0.0.20 -p 21 -m ftp:CL=1 -g CL=3
The example demonstrates the hierarchy precedence. The services that
are going to be cracked are SSH for scanme.nmap.org and FTP for hosts
10.0.0.120, 10.0.0.20. No particular timing-template has been specified
and thus the default will be used (Normal - 3). The per-host options
for scanme.nmap.org define that the minimum connection limit (cl) is 10
and that Ncrack should attempt only 1 authentication try (at) per
connection. These values would override any other for service SSH of
host scanme.nmap.org if there were conflicts with other modes. Since a
global option of -g CL=3 was defined and there is no other
higher-precedence for service SSH and scanme.nmap.org in particular,
this value will also be applied. As for the FTP targets, the per-module
-m ftp:CL=1 defined for all FTP services will override the equivalent
global one. All these can get quite complex if overused, but they are
not expected to be leveraged by the average Ncrack user anyway.
Complicated network scanning scenarios might require them, though. To
make certain the results are the ones you expect them to be, don´t
forget to use the -sL option that prints out details about what Ncrack
would crack if invoked normally. You can add the debugging -d option if
you want even more verbose output. For the above example, Ncrack would
print the following:
Example 5. Service Option Hierarchy Output example
$ ncrack scanme.nmap.org:22,cl=10,at=1 10.0.0.120 10.0.0.20 -p 21 -m ftp:CL=1 -g CL=3 -sL -d
Starting Ncrack 0.01ALPHA ( http://ncrack.org ) at 2009-08-05 18:32 EEST
----- [ Timing Template ] -----
cl=7, CL=80, at=0, cd=0, cr=10, to=0
----- [ ServicesTable ] -----
SERVICE cl CL at cd cr to ssl path
ftp:21 N/A 1 N/A N/A N/A N/A no null
ssh:22 N/A N/A N/A N/A N/A N/A no null
telnet:23 N/A N/A N/A N/A N/A N/A no null
smtp:25 N/A N/A N/A N/A N/A N/A no null
http:80 N/A N/A N/A N/A N/A N/A no null
https:443 N/A N/A N/A N/A N/A N/A yes null
----- [ Targets ] -----
Host: 64.13.134.52 ( scanme.nmap.org )
ssh:22 cl=10, CL=10, at=1, cd=0, cr=10, to=0, ssl=no, path=/
Host: 10.0.0.120
ftp:21 cl=3, CL=1, at=0, cd=0, cr=10, to=0, ssl=no, path=/
Host: 10.0.0.20
ftp:21 cl=3, CL=1, at=0, cd=0, cr=10, to=0, ssl=no, path=/
Ncrack done: 3 services would be scanned.
Probes sent: 0 | timed-out: 0 | prematurely-closed: 0
Ncrack finished.
The ServicesTable just lists the per-module options for all available
services. As you can see, the only defined option is in the FTP service
for the CL . The Targets table is the most important part of this
output and lists all targets and associated options according to the
command-line invocation. No network operation takes place in this mode,
apart from forward DNS resolution for hostnames (like scanme.nmap.org
in this example).
TIMING AND PERFORMANCE
The timing engine is perhaps the most important part of any serious
network authentication cracking tool. Ncrack´s timing engine offers a
great many options for optimization and can be bended to serve
virtually any user need. As Ncrack is progressing, this subsystem is
going to evolve into a dynamic autonomous engine that will be able to
automatically adjust its behaviour according to the network feedback it
gets, in order to achieve maximum performance and precision without any
user intervention.
Some options accept a time parameter. This is specified in seconds by
default, though you can append ‘ms’, ‘m’, or ‘h’ to the value to
specify milliseconds, minutes, or hours (‘s’ for seconds is redundant).
So the cd (connection delay) arguments 900000ms, 900s, and 15m all do
the same thing.
cl num-minconnections; CL num-maxconnections (Adjust number of
concurrent parallel connections)
Connection Limit
These options control the total number of connections that may be
outstanding for any service at the same time. Normally, Ncrack
tries to dynamically adjust the number of connections for each
individual target by counting how many drops or connection failures
happen. If a strange network condition occurs, that signifies that
something may be going wrong, like the host dropping any new
connection attempts, then Ncrack will immediately lower the total
number of connections hitting the service. However, the caps number
of the minimum or maximum connections that will take place can be
overridden using these two options. By properly adjusting them, you
can essentially optimize performance, if you can handle the tricky
part of knowing or discovering your target´s own limits. The
convention here is that cl with lowercase letters is referring to
the minimum connection limit, while CL with uppercase letters is
referring to the maximum number of connections.
The most common usage is to set cl (minimum connection limit) for
targets that you are almost certain are going to withstand these
many connections at any given time. This is a risky option to play
with, as setting it too high might actually do more harm than good
by effectively DoS-attacking the target and triggering firewall
rules that will ban your IP address.
On the other hand, for more stealthy missions, setting the CL
(maximum connection limit) to a low value might be what you want.
However, setting it too low will surely have a great impact in
overall cracking speed. For maximum stealth, this can be combined
with the cd (connection delay) described below.
at num-attempts (Adjust authentication attempts per connection)
Authentication Tries
Using this option, you can order Ncrack to limit the authentication
attempts it carries out per connection. Ncrack initially sends a
reconnaisance probe that lets it calculate the maximum number of
such authentication tries and from thereon it always tries to use
that number. Most servicse pose an upper limit on the number of
authentication per connection and in most cases finding that
maximum leads to better performance.
Setting this option to lower values can give you some stealth
bonus, since services such as SSH tend to log failed attempts after
more than a certain number of authentication tries per connection.
They use that as a metric rather than counting the total number of
authentication attempts or connections per IP address (which is
usually done by a firewall). Consequently, a number of 1 or 2
authentication tries might circumvent logging in some cases.
Note that setting that option to a high value will not have any
effect if Ncrack realizes that the server doesn´t allow that many
attempts per connection. In this case, it will just use that
maximum number and ignore your setting.
cd time (Adjust delay time between each new connection)
Connection Delay
This option essentially defines the imposed time delay between each
new connection. Ncrack will wait the amount of time you specify in
this option value, before starting a new connection against the
given service. The higher you set it, the slower Ncrack will
perform, but the stealthier your attack will become.
Ncrack by default tries to initiate new connections as fast as
possible given that new probes are actually allowed to be sent and
are not restricted by parameters such as Connection Limit which can
dynamically increase or decrease. Although this approach achieves
blazing speed as long as the host remains responsive, it can lead
to a number of disasters such as a firewall being triggered, the
targets´ or your bandwidth to be diminished and even the tested
service to suffer a Denial of Service attack. By carefully
adjusting this option, you can potentially avoid these annoying
situations.
cr max-conattempts (Adjust the max number of connection attempts)
Connection Retries
NOT IMPLEMENTED YET.
to time (Adjust the maximum overall cracking time)
Timeout
Define how much time Ncrack is going to spend cracking the service,
before giving up regardless of whether it has found any credentials
so far. However, any authentication token discovered until that
time, will be stored and printed normally. Ncrack marks a service
as finished when the username/password lists iteration ends or when
it can no longer crack it for some serious reason. If Ncrack
finishes cracking a service before the time specified in this
option, then it will not be taken into account at all.
Sometimes, you have a limited time window to scan/crack your hosts.
This might occur for various reasons. A common one would be that
normal user activity mustn´t be interrupted and since Ncrack can
become very aggressive, it might be allowed to scan the hosts only
at during certain time period like the night hours. Scanning during
certain such hours is also likely to make an attack less
detectable.
Don´t forget that Ncrack allows you to specify the time unit of
measure by appending ‘ms’, ‘m’, or ‘h’ for milliseconds, minutes or
hours (seconds is the default time unit). Using them in this
particular option, is really convenient as you can specify
something like to=8h to give Ncrack a total of 8 hours to crack
that service. Setting up cronjobs for scheduled scans in
combination with this option, might also be a good idea.
-T paranoid|sneaky|polite|normal|aggressive|insane (Set a timing
template) .
While the fine-grained timing controls discussed in the previous
section are powerful and effective, some people find them
confusing. Moreover, choosing the appropriate values can sometimes
take more time than the scan you are trying to optimize. So Ncrack
offers a simpler approach, with six timing templates. You can
specify them with the -T option and their number (0–5) or their
name. The template names are paranoid (0), sneaky (1), polite (2),
normal (3), aggressive (4), and insane (5). The first two are for
IDS evasion. Polite mode slows down the scan to use less bandwidth
and target machine resources. Normal mode is the default and so -T3
does nothing. Aggressive mode speeds scans up by making the
assumption that you are on a reasonably fast and reliable network.
Finally insane mode assumes that you are on an extraordinarily fast
network or are willing to sacrifice some accuracy for speed.
These templates allow the user to specify how aggressive they wish
to be, while leaving Ncrack to pick the exact timing values. If you
know that the network service is going to withstand a huge number
of connections you might try using the aggressive template of -T4 .
Even then, this is mostly advised for services residing in the
local network. Going over to insane mode -T5 is not recommended,
unless you absolutely know what you are doing.
While -T0. and -T1. may be useful for avoiding IDS alerts, they
will take an extraordinarily long time to crack even a few
services. For such a long scan, you may prefer to set the exact
timing values you need rather than rely on the canned -T0 and -T1
values.
--connection-limit numprobes (Adjust the threshold of total concurrent
connections)
NOT IMPLEMENTED YET.
AUTHENTICATION
This section describes ways of specifying your own username and
password lists as well as the available modes of iterating over them.
Ncrack ships in with a variety of username and password lists which
reside under the directory ´lists´ of the source tarball and later
installed under Ncrack´s data directory which usually is
/usr/local/share/ncrack or /usr/share/ncrack . You can omit specifying
any lists and Ncrack is going to use the default ones which contain
some of the most common usernames and passwords. The password list is
frequency-sorted with the top most common passwords at the beginning of
the list so they will be tried out first. The lists have been derived
from a combination of sorting publicly leaked password files and other
techniques.
-U filename (Specify username list)
Specify your own username list by giving the path to the filename
as argument to this option.
Usernames for specific environments can be gathered in numerous
ways including harvesting for email-addresses in the company´s
website, looking up information in whois databases, using the SMTP
VRFY technique at vulnerable mail servers or through social
engineering.
-P filename (Specify password list)
Specify your own password list by giving the path to the filename
as argument to this option.
Common passwords are usually derived from leaked lists as a result
of successful intrusions in public sites such as forums or other
social networking places. A great deal of them have already been
publicly disclosed and some of these have been used to assemble
Ncrack´s own lists.
--user username_list (Specify command-line comma-separated username
list)
Specify your own usernames directly in the command-line as a
comma-separated list.
--pass password_list (Specify command-line comma-separated password
list)
Specify your own passwords directly in the command-line as a
comma-separated list.
--passwords-first (Reverse the way passwords are iterated)
Ncrack by default iterates the username list for each password.
With this option, you can reverse that. For example, given the
username list of -> "root, guest, admin" and the password list of
"test, 12345, q1w2e3r4" Ncrack will normally go over them like this
-> root:test, guest:test, admin:test, root:12345 etc. By enabling
this option it will go over them like this -> root:test,
root:12345, root:q1w2e3r4, guest:test etc.
Most network authentication cracking tools prefer by default to
iterate the password list for each username. This is, however,
ineffective compared to the opposite iteration in most cases. This
holds true for the simple reason that password lists are usually
sorted on a frequency basis, meaning that the more common a
password is, the closer to the beginning of the password list it
is. Thus, iterating over all usernames for the most common
passwords first has usually more chances to get a positive result.
With the --passwords-first iteration, very common passwords might
not even be tried out for certain usernames if the user chooses to
abort the session early. However, this option might prove valuable
for cases where the attacker knows and has already verified that
the username list contains real usernames, instead of blindly
bruteforcing through them.
--pairwise (Choose usernames and passwords in pairs)
Enabling this option will make Ncrack iterate the username and
password list by choosing them in pairs. For example, given the
username list of "root, guest, admin" and the password list of
"test, 12345, q1w2e3r4" Ncrack will go over them like this:
"root:test", "guest:12345", "admin:q1w2e3r4". This is particulary
useful when inside knowledge of the infrastructure tested is
available and special username and password lists have been made.
OUTPUT
Any security tool is only as useful as the output it generates. Complex
tests and algorithms are of little value if they aren´t presented in an
organized and comprehensible fashion. Of course, no single format can
please everyone. So Ncrack offers several formats, including the
interactive mode for humans to read directly and XML for easy parsing
by software.
In addition to offering different output formats, Ncrack provides
options for controlling the verbosity of output as well as debugging
messages. Output types may be sent to standard output or to named
files, which Ncrack can append to or clobber.
Ncrack makes output available in three different formats. The default
is called interactive output, and it is sent to standard output
(stdout). There is also normal output, which is similar to interactive
except that it displays less runtime information and warnings since it
is expected to be analyzed after the scan completes rather than
interactively.
XML output is one of the most important output types, as it can be
converted to HTML, easily parsed by programs such as Ncrack graphical
user interfaces, or imported into databases. Currently, XML output
hasn´t been implemented.
While interactive output is the default and has no associated
command-line options, the other two format options use the same syntax.
They take one argument, which is the filename that results should be
stored in. Multiple formats may be specified, but each format may only
be specified once. For example, you may wish to save normal output for
your own review while saving XML of the same scan for programmatic
analysis. You might do this with the options -oX myscan.xml -oN
myscan.ncrack. While this chapter uses the simple names like myscan.xml
for brevity, more descriptive names are generally recommended. The
names chosen are a matter of personal preference. A scheme could be
using long filenames that incorporate the scan date and a word or two
describing the scan, placed in a directory named after the company that
is being scanned.
While these options save results to files, Ncrack still prints
interactive output to stdout as usual. For example, the command nmap
-oX myscan.xml [target] prints XML to myscan.xml and fills standard
output with the same interactive results it would have printed if -oX
wasn´t specified at all. You can change this by passing a hyphen
character as the argument to one of the format types. This causes
Ncrack to deactivate interactive output, and instead print results in
the format you specified to the standard output stream. So the command
nmap -oX - target will send only XML output to stdout. Serious errors
may still be printed to the normal error stream, stderr.
Unlike some Ncrack arguments, the space between the logfile option flag
(such as -oX) and the filename or hyphen is mandatory.
All of these arguments support strftime-like conversions in the
filename. %H, %M, %S, %m, %d, %y, and %Y are all exactly the same as
in strftime. %T is the same as %H%M%S, %R is the same as %H%M, and %D
is the same as %m%d%y. A % followed by any other character just yields
that character (%% gives you a percent symbol). So -oX ´scan-%T-%D.xml´
will use an XML file in the form of scan-144840-121307.xml.
Ncrack also offers options to control scan verbosity and to append to
output files rather than clobbering them. All of these options are
described below.
Ncrack Output Formats
-oN filespec (normal output) .
Requests that normal output be directed to the given filename. As
discussed above, this differs slightly from interactive output.
-oX filespec (XML output) .
Requests that XML output be directed to the given filename.
Currently this is not implemented.
-oA basename (Output to all formats) .
As a convenience, you may specify -oA basename to store scan
results in normal and XML formats at once. They are stored in
basename.ncrack, and basename.xml respectively. As with most
programs, you can prefix the filenames with a directory path, such
as ~/ncracklogs/foocorp/ on Unix or c:\hacking\sco on Windows.
Verbosity and debugging options
-v (Increase verbosity level) .
Increases the verbosity level, causing Ncrack to print more
information about the scan in progress. Credentials are shown as
they are found and more statistical information is printed in the
end. Use it twice or more for even greater verbosity.
-d [level] (Increase or set debugging level) .
When even verbose mode doesn´t provide sufficient data for you,
debugging is available to flood you with much more! As with the
verbosity option (-v), debugging is enabled with a command-line
flag (-d) and the debug level can be increased by specifying it
multiple times. Alternatively, you can set a debug level by giving
an argument to -d. For example, -d10 sets level ten. That is the
highest effective level and will produce thousands of lines, unless
your cracking session is going really slow.
Debugging output is useful when a bug is suspected in Ncrack, or if
you are simply confused as to what Ncrack is doing and why. As this
feature is mostly intended for developers, debug lines aren´t
always self-explanatory. If you don´t understand a line, your only
recourses are to ignore it, look it up in the source code, or
request help from the development list (nmap-dev). Some lines are
self explanatory, but the messages become more obscure as the debug
level is increased.
--nsock-trace level (Set nsock trace level) .
This option is meant mostly for developers as enabling it will
activate the Nsock´s library debugging output. Nsock is the
underlying library for parallel socket handling. You will have to
specify a certain level for this option. Valid range is 0 up to 10.
Usually, a level of 1 or 2 is enough to get a good overview of
network operations happening behind the scenes. Nsock prints that
information to stdout by default.
--log-errors (Log errors/warnings to normal mode output file) .
Warnings and errors printed by Ncrack usually go only to the screen
(interactive output), leaving any normal-format output files
(usually specified with -oN) uncluttered. When you do want to see
those messages in the normal output file you specified, add this
option. It is useful when you aren´t watching the interactive
output or when you want to record errors while debugging a problem.
The error and warning messages will still appear in interactive
mode too. This won´t work for most errors related to bad
command-line arguments because Ncrack may not have initialized its
output files yet.
An alternative to --log-errors is redirecting interactive output
(including the standard error stream) to a file. Most Unix shells
make this approach easy, though it can be difficult on Windows.
Miscellaneous output options
--append-output (Append to rather than clobber output files) .
When you specify a filename to an output format flag such as -oX or
-oN, that file is overwritten by default. If you prefer to keep the
existing content of the file and append the new results, specify
the --append-output option. All output filenames specified in that
Ncrack execution will then be appended to rather than clobbered.
This doesn´t work well for XML (-oX) scan data as the resultant
file generally won´t parse properly until you fix it up by hand.
MISCELLANEOUS OPTIONS
This section describes some important (and not-so-important) options
that don´t really fit anywhere else.
--resume file (Continue previously saved session) .
Whenever the user cancels a running session (usually by pressing
Ctrl+C), Ncrack saves the current state into a file which it can
later use to continue from where it had stopped. This file is saved
in subdirectory .ncrack/ of the user´s home path with a filename
format of "restore.YY-MM-DD_hh-mm". An example would be:
"/home/ithilgore/.ncrack/restore.2010-05-18_04-42". You can then
continue your session, by specifying this file as argument to the
--resume option.
-f (Quit cracking service after one found credential) .
This option will force Ncrack to quit cracking a service as soon as
it finds a valid username/password combination for it. Assuming
many parallel services are being cracked at the same time, this
option is applied on each of them separately. This means that
Ncrack will stop cracking each individual service after finding a
pair of credentials for it, but will not quit entirely. Supplying
the option two times, like -f -f will, however, make Ncrack exit
immediately as soon as it finds a valid credential for any service.
Frequently, attackers will try cracking several services in
parallel to maximize the chances of finding a pair of valid
credentials. Given that a network is no stronger than its weakest
link, this option and especially the -f -f counterpart will often
be used to lessen chances of detection and prevent network
resources from being wasted aimlessly.
-6 (Enable IPv6 scanning) .
Warning: This option was just added and it is currently
experimental, so please notify us for any problems and bugs related
to it.
The command syntax is the same as usual except that you also add
the -6 option. Of course, you must use IPv6 syntax if you specify
an address rather than a hostname. An address might look like
3ffe:7501:4819:2000:210:f3ff:fe03:14d0, so hostnames are
recommended. The output looks the same as usual, with the IPv6
address on the “Discovered credentials” line being the only IPv6
give away.
While IPv6 hasn´t exactly taken the world by storm, it gets
significant use in some (usually Asian) countries and most modern
operating systems support it. To use Ncrack with IPv6, both the
source and target of your scan must be configured for IPv6. If your
ISP (like most of them) does not allocate IPv6 addresses to you,
free tunnel brokers are widely available and will probably work
fine with Ncrack. A popular IPv6 tunnel broker service is at
http://www.tunnelbroker.net. 6to4 tunnels are another popular, free
approach.
-sL (List Scan) .
The list scan simply lists each host and service that would be
cracked if this option wasn´t specified. No packets are sent to the
target hosts and the only network operation that might happen is
DNS-resolution of any hostnames of targets. This option is really
helpful in making sure that you have specified everything as you
wanted. Service-specific options will also be printed so this acts
as a good sanity check of potentially complex command-line
arguments such as the advanced modes of Service Option
Specification and the equivalent Hierarchy for sessions that
require delicate timing handling. If list scan is called along with
the -d debug option, then additional output, like the ServicesTable
and the current Timing-Template´s parameters, is also going to be
printed.
--datadir directoryname (Specify custom Ncrack data file location) .
Ncrack needs a file called ncrack-services to load a lookup-table
of supported services/ports. This file shouldn´t be changed, unless
you know what you are doing (e.g extending Ncrack for additional
modules). In addition, Ncrack is shipped with various username and
password lists, some of which are used by default in case the user
doesn´t specify ones of his own. All these files are normally
copied during the installation procedure to a directory such as
/usr/share/ncrack or /usr/local/share/ncrack . Using the --datadir
option, will force Ncrack to start searching for these files in
specified directory. If the files aren´t found, then it will
continue searching in the directory specified by the NCRACKDIR
environmental variable NCRACKDIR (if it is defined). Next comes
~/.ncrack directory for real and effective UIDs (POSIX systems
only) or location of the Ncrack executable (Win32 only), and then a
compiled-in location such as /usr/local/share/ncrack or
/usr/share/ncrack. As a last resort, Ncrack will look in the
current directory.
--proxy type://proxy:port (Make connections via socks4, 4a, http) .
This will make Ncrack perform the authentication cracking session
through the proxy host specified.
-V; --version (Print version number) .
Prints the Ncrack version number and exits.
-h; --help (Print help summary page) .
Prints a short help screen with the most common command flags.
Running Ncrack without any arguments does the same thing.
RUNTIME INTERACTION
During the execution of Ncrack, all key presses are captured. This
allows you to interact with the program without aborting and restarting
it. Certain special keys will change options, while any other keys will
print out a status message telling you about the scan. The convention
is that lowercase letters increase the amount of printing, and
uppercase letters decrease the printing. You may also press ‘?’ for
help.
v / V
Increase / decrease the verbosity level
d / D
Increase / decrease the debugging Level
p / P
Display found credentials
?
Print a runtime interaction help screen
Anything else
Print out a status message like this:
Stats: 0:00:20 elapsed; 0 services completed (1 total)
Rate: 6.26; Found: 1; About 13.27% done; ETC: 21:06 (0:02:17
remaining)
MODULES
Ncrack´s architecture is modular with each module corresponding to one
particular service or protocol. Currently, Ncrack supports the
protocols FTP, Telnet, SSH, RDP, VNC, HTTP(S), POP3(S), SIP, Redis and
PostgreSQL. If you want to write and contribute your own Ncrack
modules, be sure to read the Ncrack Developer´s Guide at
http://nmap.org/ncrack/devguide.html Below we describe some key points
for each of them.
FTP Module
FTP authentication is quite fast, since there is very little
protocol negotiation overhead. Most FTP daemons allow 3 to 6
authentication attempts but usually impose a certain delay before
replying with the results of a failed attempt. Filezilla is one of
the most characteristic examples of this case, where the time delay
is so great, that it is usually faster to open more connections
against it, with each of them doing only 1 authentication per
connection.
Telnet Module
Telnet daemons have been largely substituded by their safer
´counterpart´ of SSH. However, there are many boxes, mainly routers
or printers, that still rely on Telnet for remote access. Usually
these are also easier to crack, since default passwords for them
are publicly known. The drawback is that telnet is a rather slow
protocol, so you shouldn´t be expecting really high rates against
it.
SSH Module
SSH is one of the most prevalent protocols in today´s networks. For
this reason, a special library, named opensshlib and based on code
from OpenSSH, was specifically built and tailored for Ncrack´s
needs. Opensshlib ships in with Ncrack, so SSH support comes out of
the box. OpenSSL will have to be installed in Unix systems though.
Windows OpenSSL dlls are included in Ncrack, so Windows users
shouldn´t be worrying about it at all.
SSH bruteforcing holds many pitfalls and challenges, and you are
well advised to read a paper that was written to explain them. The
latest version of the "Hacking the OpenSSH library for Ncrack"
document can be found under docs/openssh_library.txt or at
http://sock-raw.org/papers/openssh_library
HTTP(S) Module
The HTTP Module currently supports basic and digest authentication.
Ncrack tries to use the "Keepalive" HTTP option, whenever possible,
which leads to really high speeds, since that allows dozens of
attempts to be carried out per connection. The HTTP module can also
be called over SSL.
SMB Module
The SMB module currently works over raw TCP. NetBIOS isn´t
supported yet. This protocol allows for high parallelization, so
users could potentially increase the number of concurrent probes
against it. SMB is frequently used for file-sharing among other
things and is one of the most ubiquitous protocols, being present
in both Unix and Windows environments.
RDP Module
RDP (Remote Desktop Protocol) is a proprietary protocol developed
by Microsoft for the purpose of providing remote terminal services
by transferring graphics display information from the remote
computer to the user and transporting input commands from the user
to the remote computer. Fortunately, Microsoft recently decided to
open the protocol´s internal workings to the public and has
provided official documentation, which can be found at
http://msdn.microsoft.com/en-us/library/cc240445%28v=PROT.10%29.aspx
RDP is one of the most complex protocols, requiring the exchange of
many packets, even for just the authentication phase. For this
reason, cracking it takes a lot of time and this is probably the
slowest module. The connection phase is briefly described at
http://msdn.microsoft.com/en-us/library/cc240452%28v=PROT.10%29.aspx
where you can also see a diagram of the various packets involved.
Care must be taken against RDP servers in Windows XP versions,
since they can´t handle multiple connections at the same time. It
is advised to use a very slow timing template or even better limit
the maximum parallel connections using timing options such as CL
(Connection Limit) or cd (connection delay) against Windows XP (and
relevant) RDP servers. Windows Vista and above don´t suffer from
the same limitation.
VNC Module
The VNC protocol has known widespread usage among Unix
administrators and users for remote graphical access. VNC is
perhaps one of the most vulnerable protocols in terms of
brute-forcing, since it often requires a password without a
corresponding username for authentication. In addition, some
versions of VNC impose an 8-character limit in password length. You
should consider adding the --passwords-first option when cracking
VNC systems to exploit the fact that the username often has no
actual importance in authentication.
POP3(S) Module
POP3 support is still experimental and hasn´t been thoroughly
tested. You can expect it to work against common mail servers,
nevertheless.
SIP Module
The Session Initiation Protocol is a text-based protocol, very
similar to HTTP in its structure. The most common application of
SIP is in Internet telephony for voice and video calls. Nearly all
enterprises have infrastructure that supports conference calls and
part of them are based on SIP, making the authentication part a
significant threat vector.
Redis Module
Redis is one of the most widely used caching servers and the most
popular NoSQL database. Despite its reputation, the authentication
mechanism is very simple, only allowing for a password to protect
remote access to the service. Due to the high performance of Redis
and the fact that only 2 packets are needed for the authentication
phase, Ncrack can try a lot of passwords in parallel (‐
http://redis.io/commands/AUTH). Specifying a username list or
single username will have no effect in this module, since Redis
only deals with passwords.
PostgreSQL Module
PostgreSQL is often used as a backend database. The PostgreSQL
module supports md5 authentication, which is the most frequent
password authentication method.
MySQL Module
The MySQL module supports native authentication.
BUGS
Like its authors, Ncrack isn´t perfect. But you can help make it better
by sending bug reports or even writing patches. If Ncrack doesn´t
behave the way you expect, first upgrade to the latest version
available from http://nmap.org/ncrack. If the problem persists, do some
research to determine whether it has already been discovered and
addressed. Try searching for the error message on our search page at
http://insecure.org/search.html or at Google. Also try browsing the
nmap-dev archives at http://seclists.org/ . Read this full manual page
as well. If you are developing your own Ncrack module, make sure you
have first read the Ncrack Developer´s Guide at
http://nmap.org/ncrack/devguide.html . If nothing comes of this, mail a
bug report to nmap-dev@insecure.org . Please include everything you
have learned about the problem, as well as what version of Ncrack you
are running and what operating system version it is running on. Problem
reports and Ncrack usage questions sent to nmap-dev@insecure.org are
far more likely to be answered than those sent to Fyodor directly. If
you subscribe to the nmap-dev list before posting, your message will
bypass moderation and get through more quickly. Subscribe at
http://cgi.insecure.org/mailman/listinfo/nmap-dev .
Code patches to fix bugs are even better than bug reports. Basic
instructions for creating patch files with your changes are available
at http://nmap.org/data/HACKING . Patches may be sent to nmap-dev
(recommended) or to Fyodor directly.
AUTHORS
ithilgore (Fotis Hantzis) ithilgore.ryu.l@gmail.com (‐
http://sock-raw.org)
Fyodor fyodor@insecure.org (http://insecure.org)
NCRACK COPYRIGHT AND LICENSING
While it isn´t distributed with Nmap, Ncrack is part of the Nmap
project and falls under the same license and (non) warranty provisions,
as described at http://nmap.org/book/man-legal.html.
Ncrack 04/06/2016 NCRACK(1)
