The newest method of spreading Locky ransomware was discovered by accident when an astute user contacted security researcher Bart Blaze. The user noticed that his Facebook Messenger service had loaded a file to the account without consent or any intervention whatsoever. It totally bypassed the file extension filters that were active on the account.

One User’s Locky Day

The downloaded file, Blaze found, was a scalable vector graphic. This open standard is an XML-based vector image format for two-dimensional graphics. It also supports interactivity and animation.

Functionally, this means that any content — such as JavaScript, for example — can be embedded into the structure. A modern browser would be able to open this file and execute its contents, which was exactly what was going on.

The embedded JavaScript in the malicious file contained misdirection instructions for the browser. A browser would then run the JavaScript and end up at a fake YouTube site.

New Infection Tactics

Once there, the victim was asked to download a codec to play the mysterious content. This codec is purported to be a Chrome extension. If installed, it propagates the malware via Facebook Messenger using another poisoned image file.

CSO Online reported that the extension may also install a downloader program, called Nemucod. This malware goes out and fetches the Locky ransomware to infect the victim. This method of transmission leads to the Locky ransomware infection.

Be Wary of Locky Ransomware

Blaze recommended immediately removing the browser extension, but did not mention what to do if the browser has already been attacked by Locky and is unavailable.

He offered some further advice on his blog, however. “As always,” Blaze wrote, “be wary when someone sends you just an ‘image’ — especially when it is not how he or she would usually behave.”

Both Facebook and Google have been notified of the issue but have yet to respond.