Security researchers are warning internet users that they could fall victim to an encryption attack that permanently locks information on their PC unless they pay a ransom to hackers.
Both Websense and Symantec issued a warning of the threat, which includes the distribution of the known Pgpcoder trojan.
Websense said one type of attack, recently experienced by one of its customers, could use a known flaw in the Internet Explorer browser.
The attack happens when a user visits a malicious website, which then downloads and runs an application that encrypts files on the victim’s PC. The program finishes off by delivering a ransom note to the user.
The flaw in Internet Explorer that is exploited by such an attack has already been patched by Microsoft.
Symantec said the Pgpcoder trojan was currently the main threat to users. Pgpcoder searches for 15 common file types, including Microsoft Office files, and encrypts them. It then usually drops a message demanding $200 (£108) for the encryption key to unlock them.
Such extortion attempts aren’t currently widespread, possibly because potential attackers still have to find a way to clear the electronic money trail leading to them.