Researchers have discovered a group of premium-rate SMS trojans that share code with Spitmo, a mobile variant of the notorious banking trojan SpyEye.
The so-called “cousins of Spitmo" are premium-rate SMS trojans that target Russian users of Symbian and Windows Mobile phones.
The malware was named OpFake because the installer purports to be an updater for Opera Mini, a mobile web browser.
Once installed on a victim's phone, OpFake sends SMS messages to Russian-based premium-rate numbers without the owner's consent, F-Secure security adviser Sean Sullivan said.
The malware then prevents messages that verify the text went through from being sent back to the user's phone.
The source code used to intercept incoming messages is nearly identical to that in Spitmo.
Earlier this week, F-Secure analysts discovered 54 OpFake samples while testing a new automation system they developed to scan and analyse Symbian malware, Sullivan said.
When looking deeper into the OpFake Symbian binaries, researchers uncovered a St. Petersburg, Russia-based IP address for a server that was also storing Windows Mobile versions of OpFake.
That means the malware writers may also be targeting other mobile operating systems, Sullivan said.
“We would be pretty surprised if they didn't have some version for Android in the works, if they don't have it already,” he said.
Researchers have reported the malicious server's IP address to CERT-FI, the Finnish national computer security incident response team.