1. /
  2. Security Response/
  3. Trojan.Cryptolocker


Risk Level 1: Very Low

September 11, 2013
October 15, 2014 8:18:11 AM
Also Known As:
Trojan.Gpcoder.H [Symantec], CryptLocker.B [Norman], Trojan:Win32/Crilock.A [Microsoft], TROJ_CRILOCK.NS [Trend], Trojan.Ransomcrypt.F [Symantec]
Infection Length:
346,112 bytes
Systems Affected:
Windows XP, Windows Server 2008, Windows 7, Windows Vista, Windows Server 2003, Windows 2000
Trojan.Cryptolocker is a Trojan horse that encrypts files on the compromised computer and then prompts the user to purchase a password in order to decrypt them.

  • Virus definitions dated 11/13/2013 or earlier may detect this threat as Trojan.Ransomcrypt.F
  • Virus definitions dated 09/13/2013 or earlier may detect this threat as Trojan.Gpcoder.H

For more information, please see the following resources:

Antivirus Protection Dates

  • Initial Rapid Release version September 11, 2013 revision 022
  • Latest Rapid Release version December 24, 2014 revision 003
  • Initial Daily Certified version September 12, 2013 revision 001
  • Latest Daily Certified version December 24, 2014 revision 018
  • Initial Weekly Certified release date September 18, 2013
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment


  • Wild Level: Low
  • Number of Infections: 0 - 49
  • Number of Sites: 0 - 2
  • Geographical Distribution: Low
  • Threat Containment: Easy
  • Removal: Easy


  • Damage Level: Medium
  • Payload: Demands a ransom to decrypt files on the compromised computer.
  • Modifies Files: Encrypts files on the compromised computer.


  • Distribution Level: Low
Writeup By: Nino Fred P Gutierrez

Search Threats

Search by name
Example: W32.Beagle.AG@mm
STAR Antimalware Protection Technologies
Internet Security Threat Report
Symantec DeepSight Screensaver