According to figures collected by Kaspersky Lab, the number of new pieces of Android malware tripled between the first and second quarters of 2012.
Almost half of the new malware files were multifunctional Trojans, being capable of stealing data and downloading new malicious modules from remote servers.
One quarter were SMS Trojans, which send messages to premium-rate services without the user's consent - or even knowledge.
18% were full backdoors which give attackers full control over the device, and are used to create botnets.
2% were spyware, aimed at intercepting online banking credentials and other valuable or sensitive data.