Classification

Category: Malware

Type: -

Aliases: Mofei, W32/MoFei.worm, Backdoor.Mofeir.101, Mofeir, Worm.Win32.Mofeir

Summary


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.

Removal


Automatic action

Based on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the detected program or file, or ask you for a desired action.

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About the product

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Technical Details


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.