Mofei is a network worm with backdoor capabilities. It was discovered in the beginning of June 2003. We have received a few reports about this worm from the field.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
The worm is usually dropped to a system by SCARDSVR32.EXE file. This file is a dropper that creates the following files in Windows System fodler:
mofei.cfg navpw32.exe scardsvr32.dll
The NAVPW32.EXE file is dropped only on Windows 9x. After installation the dropper deletes itself from a hard drive.
Then the dropper copies itself with SCARDSVR32.EXE name to Windows System folder and creates a startup key for its file in System Registry:
[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run] "NavAgent32" = "<path_to_the_dropper> -v"
On NT-based computers the worm attempts to start this file as a service named SCardDrv. This way the worm's file is always active when Windows starts.
The worm spreads to computers with Windows NT-based operating systems via local network. It scans for computers with open ports 135 and 139 and if such computer is found, the worm tries to connect to IPC$ share of that computer. Mofei worm tries a few fixed passwords to get access to the IPC$ share and if it succeeds, it copies the dropper to Windows System folder on a remote computer with SCARDSVR32.EXE name and creates a service for it in System Registry.
The worm has backdoor functionalities. It contains 2 backdoor files, one for Windows 9x operating systems and the other for NT-based operating systems. A remote hacker can log into the backdoor and perform the following actions:
- show help message - show version - exit this program - change password - change port - get windows command shell - run a command - get current directionary - change directionary - list files - delete a file - make new directionary - remove a directionary - exec a DOS command - Download Internet file - bind a port - close bind
The port that the backdoor listens to is configurable. Additionally the backdoor provides information about an infected computer to a hacker.
To disinfect a system it's enough to delete all worm's files from a hard disk.
Description Created: F-Secure Anti-Virus Research Team; F-Secure Corp.; June 9th, 2003