Zotob.B is a minor variant of Zotob.A. It spreads using a vulnerability in Windows Plug and Play service (MS05-039).
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Eliminating a Local Network Outbreak
If the infection is in a local network, please follow the instructions on this webpage:
The worm is a packed PE executable file 15386 bytes long.
Installation to system
When run, the worm copies under %SYSTEM% directory using the name 'csm.exe' and creates a named mutex 'B-O-T-Z-O-R' for making sure that only one copy of the worm is run at the same time.
Then it adds the following registry entries to ensure that it is started when a user logs on or the system is restarted:
- [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices] "csm Win Updates" = "csm.exe"
The worm also adds the following registry key for diasabling shared access service:
- [HKLM\SYSTEM\CurrentControlSet\Services\SharedAccess] "Start" = "4"
Spreading using Plug and Play service vulnerability
The worm scans for systems vulnerable to Microsoft Windows Plug and Play service (MS05-039) through TCP/445.
It creates 200 threads that connect to random IP addresses within the B-class (255.255.0.0) network of the infected system. First it tests connection to port 445 and if successful, it tries to exploit the vulnerability. If the attack is successful a shell (cmd.exe) is started on port 8888. Through the shell port, the worm sends a ftp script which instructs the remote computer to download and execute the worm from the attacker computer using FTP. The FTP server listens on port 33333 on all infected computers with the purpose of serving out the worm for other hosts that are being infected. The downloaded file is saved as 'haha.exe' on disk.
Here are the summary of the ports used in attack:
- Port 445- The worm scans for systems vulnerable to PnP exploit through this port
- Port 33333- FTP server port on infected systems
- Port 8888- The command shell port opened by the exploit code
The exploit uses fixed offsets inside Windows 2000 version of umpnpmgr.dll. This means that only Windows 2000 systems (SP0-4) are affected.
Please see the following page for detailed information on the vulnerability: http://www.microsoft.com/technet/security/Bulletin/MS05-039.mspx
The worm tries to connect to IRC channel at predefined address. The attacker who knows channel password can instruct the bot to execute the following actions:
- Disconnect/reconnect from the IRC channel.
- Request system information.
- Download and execute files.
- Remove worm from the system and manipulate system security settings.
Zotob.B modifies system hosts file in order to disable access to certain sites. Following hostnames are redirected to localhost IP address (127.0.0.1):
The worm also writes the following text to hosts file:
Botzor2005 Made By .... Greetz to good friend Coder. Based On HellBot3 MSG to avs: the first av who detect this worm will be the first killed in the next 24hours!!!