Trojan-Downloader.JS.Agent.bnc

Technical Details

This Trojan downloads other files via the Internet and launches them for execution on the victim machine without the user’s knowledge or consent. The program is an HTML page which contains Java Script scenarios. It is 1527 bytes in size.

Payload

Once launched, the Trojan decrypts itself and injects its code into the memory of the process which has the following mutex in the system registry:

The Trojan then uses a vulnerability in the Microsoft.XMLHTTP ActiveX component to download a file from the following URL:

This file is 45717 bytes in size. It will be detected by Kaspersky Anti-Virus as Trojan-Downloader.Win32.Delf.jfj.

The Trojan uses the ADODB.Stream Active X component to save the downloaded file to the Windows directory as "~Temp<rnd>.tmp" (<rnd> is a randomly chosen number from 1 to 9999).

The downloaded file will then be launched for execution.

Removal instructions

If your computer does not have an up-to-date antivirus, or does not have an antivirus solution at all, follow the instructions below to delete the malicious program:

1. Use Task Manager to terminate the process shown below:
   ~Temp<rnd>.tmp
2. Delete the original Trojan file (the location will depend on how the program originally penetrated the victim machine).
3. Delete the following file:
   %WinDir%\~Temp<rnd>.tmp
4. Delete all files from %Temporary Internet Files%.
5. Disable the vulnerable ActiveX object (see How to stop an ActiveX control from running in Internet Explorer
6. Update your antivirus databases and perform a full scan of the computer (download a trial version of Kaspersky Anti-Virus).