W32.Witty.Worm

Brief Description | Characteristics | Recovery | Protection | Further Information

Brief Description:
--------------------
W32.Witty.Worm is a memory-resident automated worm that spreads through networks and specifically attacks only machines running vulnerable versions of BlackIce firewall software. It has attacked a couple of campus machines running BlackIce.

Because this worm is memory-resident and doesn't create any files on the hard drive, virus definitions won't detect it.

Characteristics:
------------------
W32.Witty.Worm uses a vulnerability in ICQ parsing by ISS products. The worm sends itself to multiple IP addresses using UDP source port 4000 and a random destination port. The worm resides in memory only, and does not create files on an infected computer. The worm also has a payload that overwrites random sectors of a random hard disk.

Note: If your computer is not running a vulnerable version of one of the affected products, then you will not be infected. Products affected by this vulnerability are listed below:

• BlackICE™ Agent for Server 3.6 ebz, ecd, ece, ecf
• BlackICE PC Protection 3.6 cbz, ccd, ccf
• BlackICE Server Protection 3.6 cbz, ccd, ccf
• RealSecure® Network 7.0, XPU 22.4 and 22.10
• RealSecure Server Sensor 7.0 XPU 22.4 and 22.10
• RealSecure Desktop 7.0 ebf, ebj, ebk, ebl
• RealSecure Desktop 3.6 ebz, ecd, ece, ecf
• RealSecure Guard 3.6 ebz, ecd, ece, ecf
• RealSecure Sentry 3.6 ebz, ecd, ece, ecf

If you are running a product that has the vulnerability, which the worm uses, we recommend that you apply the relevant patch as soon as possible. Patches for this vulnerability are available at http://www.iss.net/download/.

W32.Witty.Worm performs the following actions:

1. Sends itself to remote machines from UDP source port 4000, pretending to be a valid ICQ packet.

2. Exploits the ICQ parsing by ISS products vulnerability to gain unauthorized remote execution access to a machine using a buffer overflow. When doing so, the worm overwrites system memory and runs in the same security context as the ISS product being exploited.

3. Sends itself to 20,000 randomly generated IP addresses with random destination ports and a UDP source port of 4000.

4. Attempts to overwrite 128 sectors on one of the first eight physical hard drives, selected at random. The worm selects a random location on the hard drive and overwrites it with data from memory. If the randomly selected physical hard disk does not exist, the worm will continue.

5. Returns to step 3.

Note: The fixed part of the UDP payload is 637 bytes. However the worm randomizes the size of the datagrams it sends, presumably in an effort to evade some IDS heuristics. The actual size of the sent datagrams is between 768 and 1280 bytes.

Recovery:
-----------
1. Obtain the patch for the vulnerability from http://www.iss.net/download/.
2. Disconnect the affected computer from the network.
3. Restart the computer to remove the threat from memory.
Note: If the computer has been infected, it may not restart properly. If this occurs, Symantec Security Response recommends using a data recovery program.
4. Apply the patch.
5. Reconnect to the network.

Protection:
------------
Because this worm is memory-resident and doesn't create any files on the hard drive, virus definitions won't detect it. Apply the appropriate patch for your version of BlackIce.

Further information:
-----------------------
Further information on W32.Witty.Worm can be found at:

http://securityresponse.symantec.com/avcenter/venc/data/w32.witty.worm.html
http://www.f-secure.com/v-descs/witty.shtml
http://vil.nai.com/vil/content/v_101118.htm
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=WORM_WITTY.A



Information Systems and Computing University of Pennsylvania Comments & Questions