Published Aug 13, 2012|Updated Sep 15, 2017


Alert level: Severe Detected with Windows Defender Antivirus

Also detected as: Trojan.ADH.2 (Symantec) Trojan.Packed.22433 (Dr.Web) W32/Smalldrp.AYED (Norman)

TrojanDropper:Win32/Sirefef.gen!A is a trojan that is used to install Win32/Sirefef. It is distributed using exploits and social engineering tactics, where it is bundled with "keygens" and "cracks".

In a typical scenario, you may choose to download what they think is a "keygen" or "crack" (a program that enables software piracy by bypassing licensing or activation requirements). However, TrojanDropper:Win32/Sirefef.gen!A is also included in the download and is installed on your computer  - without your knowledge - alongside the keygen or crack. 

Caution: Win32/Sirefef is a dangerous threat that uses advanced stealth techniques in order to hinder its detection and removal. If you are infected with Sirefef, we recommend you take the following steps to remove this threat from your computer:

Before you begin you will need:

- A computer that is not infected and is connected to the Internet. You will use this computer to download a copy of the Microsoft Safety Scanner
- A blank CD, DVD or USB drive. You will use this CD, DVD or USB drive to run the Scanner on your infected computer 

  1. Download a copy of the Microsoft Safety Scanner from a clean, uninfected computer
  2. Save a copy of the Scanner on a blank CD, DVD, or USB drive
  3. Restart the infected computer
  4. Insert the CD, DVD, or USB drive into your infected computer and run the Scanner
  5. Let the Scanner clean your computer and remove any infections it finds

After running the Scanner, ensure that your antivirus product is up-to-date. You can update Microsoft security products by downloading the latest definitions at this link: Get the latest definitions.

As a consequence of being infected with this threat, you may need to repair and reconfigure some Windows security features. Please see Additional remediation steps in this entry for more information.


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