Testing for Conficker with Nmap

The latest nmap release can test Windows machines for Conficker infection. If you are running Linux, nmap may already be installed. You can download the latest nmap for OS X from http://nmap.org/book/inst-macosx.htm. You actually get more more than nmap with the .dmg: it also includes Zenmap (an X11 nmap), Ncat (good old netcat), and Ndiff (compares nmap scans). I briefly fired up Zenmap but used the command line tool for everything you'll see here.

For Linux or OS X you could also compile from source.

You need the very latest version to get the scripts that will check for Conficker. The version I used here was 4.85BETA8.

You will need to disable firewalls and security suites on the Windows machine to be checked. For absolute safety, that would mean disconnecting the machines from any external network as you'd potentially be exposed while this was shut off.

The XP machine I used here had Norton Antivirus installed, which includes an "Internet Worm Protection" component that will cause the Conficker check to fail:

nmap -PN -T4 -p139,445 -n -v --script=smb-check-vulns --script-args safe=1 192.168.1.2

Starting Nmap 4.85BETA8 ( http://nmap.org ) at 2009-04-29 16:19 EDT
NSE: Loaded 1 scripts for scanning.
Initiating Connect Scan at 16:19
Scanning 192.168.1.2 [2 ports]
Completed Connect Scan at 16:19, 2.00s elapsed (2 total ports)
NSE: Script scanning 192.168.1.2.
NSE: Script Scanning completed.
Host 192.168.1.2 is up.
Interesting ports on 192.168.1.2:
PORT    STATE    SERVICE
139/tcp filtered netbios-ssn
445/tcp filtered microsoft-ds

Read data files from: /usr/local/share/nmap
Nmap done: 1 IP address (1 host up) scanned in 2.21 seconds
 

If I scan that machine with a normal "nmap 192.168.1.2", the scan will be detected and the scanning machine will be blocked from all access for 30 minutes. Attempting to run the Conficker script after that will usually just get you a hang.

However, with the Worm protection turned off, the scripts can tell us that this machine is clean:

nmap -PN -T4 -p139,445 -n -v --script=smb-check-vulns --script-args safe=1 192.168.1.2

Starting Nmap 4.85BETA8 ( http://nmap.org ) at 2009-04-29 16:38 EDT
NSE: Loaded 1 scripts for scanning.
Initiating Connect Scan at 16:38
Scanning 192.168.1.2 [2 ports]
Discovered open port 445/tcp on 192.168.1.2
Discovered open port 139/tcp on 192.168.1.2
Completed Connect Scan at 16:38, 1.10s elapsed (2 total ports)
NSE: Script scanning 192.168.1.2.
NSE: Starting runlevel 2 scan
Initiating NSE at 16:38
Completed NSE at 16:38, 0.18s elapsed
NSE: Script Scanning completed.
Host 192.168.1.2 is up (0.00042s latency).
Interesting ports on 192.168.1.2:
PORT    STATE SERVICE
139/tcp open  netbios-ssn
445/tcp open  microsoft-ds

Host script results:
|  smb-check-vulns:  
|  MS08-067: Check disabled (remove 'safe=1' argument to run)
|  Conficker: Likely CLEAN
|_ regsvc DoS: Check disabled (add --script-args=unsafe=1 to run)

Read data files from: /usr/local/share/nmap
Nmap done: 1 IP address (1 host up) scanned in 1.56 seconds
 

If you are going to scan your entire network all at once, see How to use Nmap to scan very large networks for Conficker. However, remember that each of those machines probably has something running to prevent that, so it's not going to be all that easy usually.

Of course I also scanned the entire local network out of idle curiosity. Everything was as I expected except for these two machines:

Interesting ports on IP-STB1.home (192.168.1.100):
Not shown: 999 closed ports
PORT     STATE SERVICE
8082/tcp open  blackice-alerts

Interesting ports on IP-STB3.home (192.168.1.102):
Not shown: 999 closed ports
PORT     STATE SERVICE
8082/tcp open  blackice-alerts
 

Huh? What the heck are those? I had a moment of confusion until I realized that STB stands for "Set Top Box". Those are my Verizon TV boxes. It's interesting that they appear to be running a Black-Ice firewall. I wonder if my scan tripped any alarms?

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Wed Apr 29 23:54:34 2009: Subject:   drag


"""
Huh? What the heck are those? I had a moment of confusion until I realized that STB stands for "Set Top Box". Those are my Verizon TV boxes. It's interesting that they appear to be running a Black-Ice firewall. I wonder if my scan tripped any alarms?
"""

I really doubt that the people that work on those crappy set-top boxes are really up to that level of sophistication.

Point your telnet or browser at that port and see what happens.



Thu Apr 30 00:43:47 2009: Subject:   TonyLawrence


Well, somewhere somebody has to be concerned about network security.. :-)



Thu Apr 30 14:20:58 2009: Subject:   jtimberman


While scanning your home network is a great idea, if you're in a company environment, be careful about scanning systems. Make sure you have written permission from someone with authorization to permit such scans. Nmap scans can cause wild things to happen. In some cases, printers will spit out reams of paper or applications will stop responding. You'll need to disclaim liability for that.




Thu Apr 30 15:49:47 2009: Subject:   TonyLawrence


Yes, good point. There have been times when I really could have used a nmap scan but went without it because I couldn't find the right people to approve it.

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