Threat Description

Winshell

Details

Aliases: Winshell, Backdoor.Winshell
Category: Malware
Type: Backdoor
Platform: W32

Summary


Backdoor.Winshell is a hacker's tool that allows an attacker to remotely control a computer where it is installed. An attacker just has to telnet to the preconfigured port of the remote computer and a menu is shown.



Removal


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.

More

Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.



Technical Details


This backdoor's file is packed with UPX file compressor, the port it listens to is configurable. It allows the following operations to be performed on an infected computer:

1. Install the backdoor so that it will be launched next time Windows starts.

2. Removes the entries created when installing from the Windows registry.

3. Reboot a computer.

4. Open a shell that allows a computer to be controlled remotely.

5. Download any file from a given URL.

When creating a shell, the backdoor executes cmd.exe or command.com command interpreter, depending on Windows version, and pipes its output to the attacker.

All files detected as Backdoor.Winshell should be deleted from an infected system. If some files are locked while Windows is active, they should be deleted from pure DOS (in case of Windows 9x system) or renamed with a different extension (.EXA for example) with further system restart (in case of NT-based system). After restart the renamed file should be deleted.





Description Details: Ero Carrera; F-Secure Corp.; July 24th, 2002


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