The worm is a packed PE executable file 22528 bytes long.
When run, the worm saves a copy of itself to the System directory using the name "botzor.exe" and creates a mutex named "B-O-T-Z-O-R" to ensure only one copy of the worm is run at any one time.
It then 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] "WINDOWS SYSTEM" = "botzor.exe"
The worm also adds the following registry key to diasable shared access service:
- [HKLM\SYSTEM\CurrentControlSet\Services\SharedAccess] "Start" = "4"
To propagate itself, the worm scans for systems vulnerable to Microsoft Windows Plug and Play service (MS05-039) through TCP/445. 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
To scan for vulnerable systems, Zotob creates 300 threads that connect to random IP addresses within the B-class (255.255.0.0) network of the infected system. It first tests connection to port 445 and if successful, it tries to exploit the vulnerability.
If the attack is successful, a command shell is started on the remote computer's 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.
All infected computers listen on port 33333 in order to serve out the worm to other hosts being infected. The downloaded file is saved as 'haha.exe' on disk.
Here is 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 worm tries to connect to a predefined IRC channel. An 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
- Manipulate the system security settings.
Zotob.A modifies the system hosts file to disable access to certain sites. The 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!!!