A new ransomware variant encrypts files on a computer but uses a novel twist on monetizing the extortion threat, according to researchers at Symantec.
Instead of demanding money directly for decryption keys, as has been the case in other instances, it presumes that the owner of an infected computer will search for information to help unlock the files. The search typically leads to a fraudulent company offering a fix but requiring a payment to obtain it.
The malware was found by Shunichi Imano, an engineer with Symantec Security Response. In a blog post Friday, he said that the malicious software, called Trojan.Ramvicrype, uses the RC4 algorithm, a widely-used software cipher, to encrypt files on compromised computers, rendering them unusable.
Once on a victim’s machine, the trojan encrypts files in recently opened locations, Imano said.
“One of the worst-case scenarios occurs when a file in the Windows system folder has recently been opened,” he said. “This leads to a situation in which the threat encrypts all files in the Windows system folder, the computer is critically damaged and the user is unlikely to be able to access the internet to search for the fix.”
Ransomware typically display a message demanding users pay online criminals in exchange for keys that can be used to unlock a computer or decrypt any encrypted files. One case last year involved malicious ads that were able to evade detection scans run by websites or third-party ad networks.
To help prevent infections such as these, Symantec recommends that users take standard precautions, such as using complex passwords, ensuring that programs use the lowest level of privileges necessary, disabling file sharing if not needed, keeping patches up-to-date and isolating compromised computers quickly to prevent threats from spreading.
Symantec has posted a fix for the Trojan.Ramvicrype infection here.