The Android operating system accounted for 79 percent of all malware infections on smartphones, F-Secure said Thursday.

According to the security firm's Mobile Threat Report Q4 2012, 301 total new threat families and variants were detected in 2012. Android malware continued to gain in its share, responsible for 79 percent of all threats for the year, up from 66 percent in 2011.

In what may be the only good news for Symbian, F-Secure's report shows a drop in malware targeting the declining platform to just four percent of all mobile threats detected in the fourth quarter of 2012, down from an average of 26 percent in the first three quarters. Malware targeting Symbian was down to 19 percent of all mobile malware for the year 2012, down from 29 percent in 2011.

The numbers are starkly reversed from 2010, when Symbian malware accounted for 62 percent of threats and Android just 11 percent.

66 percent of mobile malware detections in 2012 were trojans, a number Sean Sullivan, security advisor at F-Secure Labs, expects to drop in the coming year with Google's release of Android 4.2 Jellybean late last year. The extra security prompts when downloading in 4.2 should help deflect trojans, and as spying and monitoring tools increasingly become part of the mix, surveillance-related threats will account for a greater portion, he says.

A large share of the Android threats found in Q4 were malware that generate profit through fraudulent SMS practices. 21 of the 96 Android threat variants found were contributed by Premium SMS, a malware family that sends out messages to premium rate numbers. Many more Android threats employ similar tactics, some signing up the victim to an SMS-based subscription service. Messages or notifications from these numbers and services are deleted, keeping the user unaware until charges appear on their bills.