Cyber-criminals are increasingly targeting online games in an effort to rob players of virtual assets and sell them on auction websites.

Security vendor Trend Micro identified more than 3,600 spyware attacks last year designed to gather log-in and password information for online games such as Second Life, Lineage and World of Warcraft. 

The password stealers are often spread through spam messages where they are presented as virtual goods or popular media content such as music or movie files.

The thieves can then auction off virtual currencies and accessories such as clothing and weapons.

World of Warcraft avatars can fetch several hundred dollars on auction sites. After the auction has ended, the seller and buyers will meet each other inside the game to handle the final transaction.