Fergie's Tech Blog

Update: MS05-039 Worm in the wild

From the SANS Internet Storm Center:

Starting around 11:30 UTC, we've received several reports on a new worm variant that makes use of MS05-039 to spread. If you're not patched yet, this is your last call.

F-Secure named the critter "Zotob.A",http://www.f-secure.com/weblog/

We've also received a submission of a binary called "pnpsrv.exe", which is recognized by ClamAV as Trojan.Spybot-123. Another reader has contributed evidence that a successful exploit by Zotob.A (or variant)

The worm will download the main payload from the infecting machine. Once a machine is infected, it will become an ftp server itself. It will scan for open port 445/tcp. Once it finds a system with port 445 listening, it will try to use the PnP exploit to download and execute the main payload via ftp.

Important facts so far:
- Patch MS05-039 will protect you
- Windows XP SP2 and Windows 2003 can not be exploited by this worm, as the worm does not use a valid logon.
- Blocking port 445 will protect you (but watch for internal infected systems)
- The FTP server does not run on port 21. It appears to pick a random high port.


Quick FTP log:

open aaa.bbb.ccc.ddd 31656
user 1 1
get winpnp.exe


quit

(IP address obfuscated).

We'll keep adding to this diary as new information becomes available.

Thanks so far to Johnathan Norman from Alert Logic for a lot of the details.
Other good information can be found at the F-Sececure weblog athttp://www.f-secure.com/weblog/
Also see the Microsoft MS05-039 bulletin from last week:http://www.microsoft.com/technet/security/Bulletin/MS05-039.mspx

Please submit any new code captures via our contact page:
http://isc.sans.org/contact.php
If possible, do not pack/encrypt the uploads, maybe provide an md5 sum to preserve the code in its original beauty.

Shown below are Snort rules, submitted by the members of the Alert Logic Security Research Team:
Jeremy Hewlett, Technical Director of Security Research
Johnathan Norman, Sr. Security Analyst
Chris Baker, Technical Director of Security Operations


alert tcp any any -> any 445 (msg:"EXPLOIT SMB-DS Microsoft Windows 2000 Plug and Play Vulnerability"; flow:to_server,established; content:"|FF|SMB%"; dept h:5; offset:4; nocase; content:"|2600|"; depth:2; offset:65; content:"|67157a76|";reference:url,www.microsoft.com/technet/security/Bulletin/MS05-039.mspx; classtype:attempted-admin; sid:1000130; rev:1;)

alert tcp any any -> any 139 (msg:"EXPLOIT NETBIOS SMB Microsoft Windows 2000 PNP Vuln"; flow:to_server,established; content:"|FF|SMB%"; depth:5;offset:4; nocase; content:"|2600|"; depth:2; offset:65; content:"|3600|"; offset:110; within:5; content:"|F6387A76|";reference:url,www.microsoft.com/technet/security /Bulletin/MS05-039.mspx; classtype:attempted-admin; sid:1000131; rev:1;)

alert tcp any any -> any 445 (msg:"EXPLOIT NETBIOS SMB-DS Microsoft Windows 2000 PNP Vuln"; flow:to_server,established; content:"|FF|SMB%"; depth:5;offset: 4; nocase; content:"|2600|"; depth:2; offset:65; content:"|3600|"; offset:110; within:5; content:"|F6387A76|";reference:url,www.microsoft.com/technet/secur ity/Bulletin/MS05-039.mspx; classtype:attempted-admin; sid:1000132; rev:1;)

We now have reports of an attack against the MS05-039 vulnerability. We have updated our security advisory located at:

http://www.microsoft.com/technet/security/advisory/899588.mspx

To provide our intitial information and guidance.

More information shortly.

posted by Fergie @ 8/14/2005 12:47:00 PM