The notorious Cryptolocker ransomware, which strongly encrypts victims’ hard drives until a ransom is paid, has taken a turn for the worse — it’s evolved from a Trojan into a worm.

This means the uncrackable malware can now propagate itself, rather than relying on gullible humans to open infected email attachments or point their browsers at corrupted Web pages.

“This update is considered significant because this routine was unheard of in other CRILOCK variants,” wrote security firm Trend Micro in a recent blog posting, using the company’s own name for the malware. “The addition of propagation routines means that the malware can easily spread, unlike other known CRILOCK variants.”