Malware defence company F-Secure has identified three Chinese companies as being behind the "Sexy Space" trojan. The virus, which got through the Symbian Foundation's digital signing process, spreads itself by text message.
For applications to work on S60 handsets, they have to pass the Symbian Foundation's automatic checks. Some are then randomly selected for human checking - in this case, the Sexy Space virus wasn't.
The trojan allows attackers to send a link via text message which would download the worm. The virus then can send similar text messages to all your contacts, costing you whatever your message fee is per contact. That could be a significant sum.
F-Secure claims this is the first identified SMS worm, and blames XiaMen Jinlonghuatian Technology, ShenZhen ChenGuangWuXian Technology, and XinZhongLi TianJin for its creation. Although it's not currently widespread, there are a few reports of its existence in China and the Middle East. All Symbian S60 phones are potential targets.
It's also worth noting, for completeness, that F-Secure sells antivirus software for Symbian devices, so it's in the company's interest to spread information about phone viruses.