Nmap smb-os-discovery NSE Script


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

Script Overview

Script source code: https://github.com/nmap/nmap/tree/master/scripts/smb-os-discovery.nse
Script categories: default, discovery, safe
Target service / protocol: smb, netbios, tcp, udp
Target network port(s): 137, 139, 445
List of CVEs: -

Script Description

The smb-os-discovery.nse script attempts to determine the operating system, computer name, domain, workgroup, and current time over the SMB protocol (ports 445 or 139). This is done by starting a session with the anonymous account (or with a proper user account, if one is given; it likely doesn't make a difference); in response to a session starting, the server will send back all this information.

The following fields may be included in the output, depending on the circumstances (e.g. the workgroup name is mutually exclusive with domain and forest names) and the information available:

  • OS
  • Computer name
  • Domain name
  • Forest name
  • FQDN
  • NetBIOS computer name
  • NetBIOS domain name
  • Workgroup
  • System time

Some systems, like Samba, will blank out their name (and only send their domain). Other systems (like embedded printers) will simply leave out the information. Other systems will blank out various pieces (some will send back 0 for the current time, for example).

If this script is used in conjunction with version detection it can augment the standard nmap version detection information with data that this script has discovered.

Retrieving the name and operating system of a server is a vital step in targeting an attack against it, and this script makes that retrieval easy. Additionally, if a penetration tester is choosing between multiple targets, the time can help identify servers that are being poorly maintained (for more information/random thoughts on using the time, see http://www.skullsecurity.org/blog/?p=76.

Although the standard smb* script arguments can be used, they likely won't change the outcome in any meaningful way. However, smbnoguest will speed up the script on targets that do not allow guest access.

Smb-os-discovery NSE Script Arguments

This is a full list of arguments supported by the smb-os-discovery.nse script:

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.

randomseed

Set to a value to change the filenames/service names that are randomly generated.

smbbasic

Forces the authentication to use basic security, as opposed to "extended security". Against most modern systems, extended security should work, but there may be cases where you want to force basic. There's a chance that you'll get better results for enumerating users if you turn on basic authentication.

smbport

Override the default port choice. If smbport is open, it's used. It's assumed to be the same protocol as port 445, not port 139. Since it probably isn't possible to change Windows' ports normally, this is mostly useful if you're bouncing through a relay or something.

smbsign

Controls whether or not server signatures are checked in SMB packets. By default, on Windows, server signatures aren't enabled or required. By default, this library will always sign packets if it knows how, and will check signatures if the server says to. Possible values are:

  • force: Always check server signatures, even if server says it doesn't support them (will Probably fail, but is technically more secure).
  • negotiate: [default] Use signatures if server supports them.
  • ignore: Never check server signatures. Not recommended.
  • disable: Don't send signatures, at all, and don't check the server's. not recommended. More information on signatures can be found in smbauth.lua.

- - -
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=smb-os-discovery --script-args smbdomain=value,smbhash=value <target>

Smb-os-discovery NSE Script Example Usage

Here's an example of how to use the smb-os-discovery.nse script:

nmap --script smb-os-discovery.nse -p445 127.0.0.1

sudo nmap -sU -sS --script smb-os-discovery.nse -p U:137,T:139 127.0.0.1

Smb-os-discovery NSE Script Example Output

Here's a sample output from the smb-os-discovery.nse script:

Host script results:
| smb-os-discovery:
|   OS: Windows Server (R) 2008 Standard 6001 Service Pack 1 (Windows Server (R) 2008 Standard 6.0)
|   OS CPE: cpe:/o:microsoft:windows_2008::sp1
|   Computer name: Sql2008
|   NetBIOS computer name: SQL2008
|   Domain name: lab.test.local
|   Forest name: test.local
|   FQDN: Sql2008.lab.test.local
|   NetBIOS domain name: LAB
|_  System time: 2011-04-20T13:34:06-05:00

Smb-os-discovery NSE Script Example XML Output

Here's a sample XML output from the smb-os-discovery.nse script produced by providing the -oX <file> Nmap option:

 <elem key="os">Windows Server (R) 2008 Standard 6001 Service Pack 1</elem>
 <elem key="cpe">cpe:/o:microsoft:windows_2008::sp1</elem>
 <elem key="lanmanager">Windows Server (R) 2008 Standard 6.0</elem>
 <elem key="domain">LAB</elem>
 <elem key="server">SQL2008</elem>
 <elem key="date">2011-04-20T13:34:06-05:00</elem>
 <elem key="fqdn">Sql2008.lab.test.local</elem>
 <elem key="domain_dns">lab.test.local</elem>
 <elem key="forest_dns">test.local</elem>

Author

  • Ron Bowes

References

See Also

Related NSE scripts to the smb-os-discovery.nse script:

Visit Nmap NSE Library for more scripts.

Version

This page has been created based on Nmap version 7.92.