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Danger level 7
Type: Trojans
Common infection symptoms:
  • Connects to the internet without permission
  • Installs itself without permissions
  • Slow Computer
  • Slow internet connection
  • System crashes


There are malicious computer programs that have many different versions in order to infect as many computers as possible. The same thing could be applied to Trojan:Win64/Sirefef.C that belongs to the big Sirefef Trojan family. This Trojan is designed to connect to a remote server without your knowledge or permission. When it connects to the remote host it downloads additional malware onto your computer or other components for the Sirefef Trojans.

Unfortunately, there is no exact way to determine whether you have been infected with to Trojan:Win64/Sirefef.C, because this parasite does not have an interface. Your best call would be monitoring your computer performance, in hope of noticing some weird behavior. For example, if your computer is being slower than usual, or if you cannot run some of your programs all of a sudden, that might be the sign that you are infected with to Trojan:Win64/Sirefef.C. Also, this Trojan will always drop a file called “X” in a randomly named folder, for example: C:\Documents and Settings\Administrator\Local Settings\Application Data\936d2a1d\X.

Upon the installation this Trojan has been observed to add a key into the registry that allows it to start automatically whenever the computer is turned. Thus the Trojan runs in your system’s background, performing its evil deeds. It connects to the remote server (e.g. and downloads other malicious components that might hijack the computer processes and trespass your privacy. Therefore, it is more than obvious that with Trojan:Win64/Sirefef.C in your system you are susceptible to other infections that might eventually lead to an ultimate system crash. Check your Windows Task Manager to see whether you have ydze.exe and igfxtrey.exe are running there. These process files are parts of Trojan:Win64/Sirefef.C, and if you have them in your Task Manager than you have the Trojan as well.

Get yourself a reliable security product that will remove Trojan:Win64/Sirefef.C automatically, and you will not have to worry about this infection again. Also, perform a full system scan for any other parasites that the Trojan might have brought along.

Download Spyware Removal Tool to Remove* Trojan:Win64/Sirefef.C
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How to manually remove Trojan:Win64/Sirefef.C

Files associated with Trojan:Win64/Sirefef.C infection:


Trojan:Win64/Sirefef.C DLL's to remove:


Trojan:Win64/Sirefef.C processes to kill:


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