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  4. Tenga.A

Tenga.A

Name : Tenga.A
Category:Malware
Type:Virus, Net-Worm
Platform:W32

Summary

Tenga.A is a virus that infects files by appending itself to each Windows executable file it finds. The virus also has the ability to scan the network and infect files found in open network shares.

Disinfection

Tenga is a network-aware parasitic file infector, so the following steps should be taken to disinfect it:
  • Stop network sharing or kill all network connections
  • Set 'Disinfect Automatically' disinfection action for on-access (real-time) scanner of F-Secure Anti-Virus
  • Scan all available hard drives with F-Secure Anti-Virus
  • Disinfect all infected files, delete or rename all undisinfectable files (you have to select 'Delete' or 'Rename' action manually if required)
  • Restart the computer
  • Scan all hard drives again to make sure that there are no more infected files left, repeat disinfection procedure if necessary
  • Disinfect all infected computers connected to the same network
  • Re-enable sharing or reconnect to the network.


Please note that a single infected computer can re-infect the whole network. So make sure that all infected computers are cleaned before they are reconnected to the network.

It is recommended to check whether Windows operating system on all computers has every necessary service pack and security updates. The missing updates and service packs should be installed if needed.

It is also recommended to set strong network share passwords. This greatly limits the spreading of network-aware worms.

Additional Details

Tenga.A infects files by appending itself to each Windows executable file it finds. The virus also has the ability to scan the network and infect files found in open network shares.

Upon execution, it connects to and tries to download and execute http://utenti.lycos.it/[***]/dl.exe. It also connects to http://[***].users.freebsd.at and opens a remote command shell on the affected machine on port 54321.

The virus uses CRC matching to search for the required APIs it needs to do its malicious tasks. It avoids infecting ntoskrnl.exe and marks each infected executable files with the character `V´ in the old DOS stub header. The marking of the infected files prevents re-infection attempts


Tenga.A also elevates its privileges and disables Windows File Protection.

To check if an instance of itself is already running, the virus creates a mutex named gaelicum.


Detection

F-Secure Anti-Virus detects this malware with the following updates:

[FSAV_Database_Version]
Version = 2005-07-14_01.