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Trojan:W32/Ransomcrypt

First posted on 22 July 2013.
Source: F-Secure

Aliases :

There are no other names known for Trojan:W32/Ransomcrypt.

Explanation :

Trojan:W32/Ransomcrypt is ransomware that encrypts files on the affected computer and demands payment, supposedly to provide a password decrypting the affected files.

Technical Details
Trojan:W32/Ransomcrypt is ransomware that encrypts files on the affected computer, alledgedly because the user is "using unlicensed programms!", according to a text file note left by the malware author:

Image 1: Ransom demand made by Trojan:W32/Ransomcrypt

When first run on the system, Trojan:W32/Ransomcrypt will drop a randomly-named copy of itself in the %temp% folder; it will also iterate all folders on the system. Every document, image and shortcut file it finds will be encrypted and appended with the extension, .EnCiPhErEd:

Image 2: Files encrypted by Trojan:W32/Ransomcrypt

In each folder, the trojan will also drop a file named "HOW TO DECRYPT.TXT" (seeImage 1) that contains instructions on how to proceed with payment to remove the encryption.

Ransomcrypt will then create registry entries to associate the .EnCiPhErEd extension with itself so that the copy in %temp% will be launched whenever the encrypted files are run and demand the password to decrypt the files:

Image 3: Password prompt from Trojan:W32/Ransomcrypt

After 5 tries it will no longer accept passwords. And it then deletes itself, leaving the files encrypted.

Last update 22 July 2013

 

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