A worm with variants known as "chode," "foreskin," "dickhair", "firkin," or "911" has received some attention over the last week. The National Infrastructure Protection Center issued a bulletin regarding this worm, available at
This worm spreads by taking advantage of unprotected Windows shares. For more information on a similar problem and relevant solutions, please see
The "chode" worm affects Windows 98 systems with unprotected shares. It does not function properly on Windows NT systems. We have not completed testing on Windows 95 systems or Windows 2000 systems.
As of this writing, CERT/CC has not received any direct reports of systems infected with this worm, though we have received a small number of second-hand reports.
The worm consists of several batch files, and it takes the following steps.
CHODE.BAT calls RANDOM.BAT, which picks a target network and initial host from a set of predefined networks.
Once RANDOM.BAT picks an initial machine, CHODE.BAT increments over the addresses, and for each address it
If it maps C and finds win.com, it then
If chode is not found, it begins the process of trying to infect/replicate. It
If the copy is successful, it
It then selects a random number based on the time. During this process, it creates a file called "cu##ent.bat", a file called "current.bat", and an environment variable called "time".
Based on the random number, it appends a file named "chocher.bat" to autoexec.bat with probability 1/10. The new autoexec.bat (with chocher.bat appended) then
Chode then copies ashield.pif, netstat.pif, and winsock.vbs to the startup folder on the victim machine. When Windows next starts on the victim machine, these files begin the process again.
The winsock.vbs file then deletes all files on the C drive on the 19th day of the month.
The initiating machine then starts again with a new IP address.
We encourage you to read CERT Incident Note IN-2000-02 for information on general solutions to the problem of unprotected Windows shares.
One notable variant (foreskin) of the worm described in this document randomly copies one of a set of batch files (named A.BAT, B.BAT, C.BAT...J.DAT) to a file called MSTUM.BAT. Other variants named dickhair and firkin are similar.
Author: Shawn Hernan