Nmap smtp-brute NSE Script


This page contains detailed information about how to use the smtp-brute NSE script. For list of all NSE scripts, visit the Nmap NSE Library.

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Overview
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Script Overview

Script source code: https://github.com/nmap/nmap/tree/master/scripts/smtp-brute.nse
Script categories: brute, intrusive
Target service / protocol: smtp, smtps, submission
Target network port(s): 25, 465, 587
List of CVEs: -

Script Description

The smtp-brute.nse script performs brute force password auditing against SMTP servers using either LOGIN, PLAIN, CRAM-MD5, DIGEST-MD5 or NTLM authentication.

Smtp-brute NSE Script Arguments

This is a full list of arguments supported by the smtp-brute.nse script:

smtp-brute.auth

Authentication mechanism to use LOGIN, PLAIN, CRAM-MD5, DIGEST-MD5 or NTLM

creds.global

Credentials to be returned by Credentials.getCredentials regardless of the service.

creds.[service]

Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password

passdb

The filename of an alternate password database. Default: nselib/data/passwords.lst

unpwdb.passlimit

The maximum number of passwords passwords will return (default unlimited).

unpwdb.timelimit

The maximum amount of time that any iterator will run before stopping. The value is in seconds by default and you can follow it with ms, s, m, or h for milliseconds, seconds, minutes, or hours. For example, unpwdb.timelimit=30m or unpwdb.timelimit=.5h for 30 minutes. The default depends on the timing template level (see the module description). Use the value 0 to disable the time limit.

unpwdb.userlimit

The maximum number of usernames usernames will return (default unlimited).

userdb

The filename of an alternate username database. Default: nselib/data/usernames.lst

brute.credfile

A file containing username and password pairs delimited by '/'

brute.delay

The number of seconds to wait between guesses (default: 0)

brute.emptypass

Guess an empty password for each user (default: false)

brute.firstonly

Stop guessing after first password is found (default: false)

brute.guesses

The number of guesses to perform against each account. (default: 0 (unlimited)). The argument can be used to prevent account lockouts.

brute.mode

Can be user, pass or creds and determines what mode to run the engine in.

  • user - the unpwdb library is used to guess passwords, every password Password is tried for each user. (The user iterator is in the outer loop)
  • pass - the unpwdb library is used to guess passwords, each password Is tried for every user. (The password iterator is in the outer loop)
  • creds - a set of credentials (username and password pairs) are Guessed against the service. This allows for lists of known or common username and password combinations to be tested. If no mode is specified and the script has not added any custom iterator the pass mode will be enabled.

brute.passonly

Iterate over passwords only for services that provide only a password for authentication. (default: false)

brute.retries

The number of times to retry if recoverable failures occur. (default: 2)

brute.start

The number of threads the engine will start with. (default: 5).

brute.threads

The number of initial worker threads, the number of active threads will be automatically adjusted.

brute.unique

Make sure that each password is only guessed once (default: true)

brute.useraspass

Guess the username as password for each user (default: true)

creds.[service]

Credentials to be returned by Credentials.getCredentials for [service]. E.g. creds.http=admin:password

smbdomain

The domain to log in with. If you aren't in a domain environment, then anything will (should?) be accepted by the server.

smbhash

A password hash to use when logging in. This is given as a single hex string (32 characters) or a pair of hex strings (both 32 characters, optionally separated by a single character). These hashes are the LanMan or NTLM hash of the user's password, and are stored on disk or in memory. They can be retrieved from memory using the fgdump or pwdump tools.

smbnoguest

Use to disable usage of the 'guest' account.

smbpassword

The password to connect with. Be cautious with this, since some servers will lock accounts if the incorrect password is given. Although it's rare that the Administrator account can be locked out, in the off chance that it can, you could get yourself in trouble. To use a blank password, leave this parameter off altogether.

smbtype

The type of SMB authentication to use. These are the possible options:

  • v1: Sends LMv1 and NTLMv1.
  • LMv1: Sends LMv1 only.
  • NTLMv1: Sends NTLMv1 only (default).
  • v2: Sends LMv2 and NTLMv2.
  • LMv2: Sends LMv2 only.
  • NTLMv2: Doesn't exist; the protocol doesn't support NTLMv2 alone. The default, NTLMv1, is a pretty decent compromise between security and compatibility. If you are paranoid, you might want to use v2 or lmv2 for this. (Actually, if you're paranoid, you should be avoiding this protocol altogether!). If you're using an extremely old system, you might need to set this to v1 or lm, which are less secure but more compatible. For information, see smbauth.lua.

smbusername

The SMB username to log in with. The forms "DOMAIN\username" and "username@DOMAIN" are not understood. To set a domain, use the smbdomain argument.

smtp.domain

The domain to be returned by get_domain, overriding the target's own domain name.

- - -
To use these script arguments, add them to the Nmap command line using the --script-args arg1=value,[arg2=value,..] syntax. For example:

nmap --script=smtp-brute --script-args smtp-brute.auth=value,creds.global=value <target>

Smtp-brute NSE Script Example Usage

Here's an example of how to use the smtp-brute.nse script:

nmap -p 25 --script smtp-brute <host>

Smtp-brute NSE Script Example Output

Here's a sample output from the smtp-brute.nse script:

PORT    STATE SERVICE REASON
25/tcp  open  stmp    syn-ack
| smtp-brute:
|   Accounts
|     braddock:jules - Valid credentials
|     lane:sniper - Valid credentials
|     parker:scorpio - Valid credentials
|   Statistics
|_    Performed 1160 guesses in 41 seconds, average tps: 33

Smtp-brute NSE Script Example XML Output

There is no sample XML output for this module. However, by providing the -oX <file> option, Nmap will produce a XML output and save it in the file.xml file.

Author

  • Patrik Karlsson

References

See Also

Related NSE scripts to the smtp-brute.nse script:

Visit Nmap NSE Library for more scripts.

The smtp-brute.nse script may fail with the following error messages. Check for the possible causes by using the code snippets highlighted below found in the script source code. This can often times help in identifying the root cause of the problem.

Incorrect password

Here is a relevant code snippet related to the "Incorrect password" error message:

87:	      local err = brute.Error:new( err )
88:	      -- This might be temporary, set the retry flag
89:	      err:setRetry( true )
90:	      return false, err
91:	    end
92:	    return false, brute.Error:new( "Incorrect password" )
93:	  end,
94:	
95:	  -- Disconnects from the server (release the connection object back to
96:	  -- the pool)
97:	  disconnect = function( self )

Failed to connect to SMTP server

Here is a relevant code snippet related to the "Failed to connect to SMTP server" error message:

103:	local function fail (err) return stdnse.format_output(false, err) end
104:	
105:	action = function(host, port)
106:	
107:	  local socket, response = smtp.connect(host, port, { ssl = true, recv_before = true })
108:	  if ( not(socket) ) then return fail("Failed to connect to SMTP server") end
109:	  local status, response = smtp.ehlo(socket, smtp.get_domain(host))
110:	  if ( not(status) ) then return fail("EHLO command failed, aborting ...") end
111:	  local mechs = smtp.get_auth_mech(response)
112:	  if ( not(mechs) ) then
113:	    return fail("Failed to retrieve authentication mechanisms form server")

EHLO command failed, aborting ...

Here is a relevant code snippet related to the "EHLO command failed, aborting ..." error message:

105:	action = function(host, port)
106:	
107:	  local socket, response = smtp.connect(host, port, { ssl = true, recv_before = true })
108:	  if ( not(socket) ) then return fail("Failed to connect to SMTP server") end
109:	  local status, response = smtp.ehlo(socket, smtp.get_domain(host))
110:	  if ( not(status) ) then return fail("EHLO command failed, aborting ...") end
111:	  local mechs = smtp.get_auth_mech(response)
112:	  if ( not(mechs) ) then
113:	    return fail("Failed to retrieve authentication mechanisms form server")
114:	  end
115:	  smtp.quit(socket)

Failed to retrieve authentication mechanisms form server

Here is a relevant code snippet related to the "Failed to retrieve authentication mechanisms form server" error message:

108:	  if ( not(socket) ) then return fail("Failed to connect to SMTP server") end
109:	  local status, response = smtp.ehlo(socket, smtp.get_domain(host))
110:	  if ( not(status) ) then return fail("EHLO command failed, aborting ...") end
111:	  local mechs = smtp.get_auth_mech(response)
112:	  if ( not(mechs) ) then
113:	    return fail("Failed to retrieve authentication mechanisms form server")
114:	  end
115:	  smtp.quit(socket)
116:	
117:	  local mech_prio = stdnse.get_script_args("smtp-brute.auth")
118:	  mech_prio = ( mech_prio and { mech_prio } ) or

Version

This page has been created based on Nmap version 7.92.

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