Security experts warned today that hackers are fast extending their efforts beyond Windows and are actively targeting Mac users.

The 2008 Security Threat Report from Sophos said that organised criminal gangs have "arrived at Apple's doorstep with the intention of stealing money".

The report acknowledged that, while malware for Macs has long existed, criminal gangs have not felt the need to target Mac users when there are so many poorly protected Windows PCs available.

But Sophos warned that Mac malware is now being written by financially-motivated hackers who see a viable and profitable market in infecting Macs alongside Windows PCs.

Many versions of the malicious OSX/RSPlug Trojan, first seen in November 2007, have been planted on websites designed to exploit Apple Mac computers for the purposes of phishing and identity theft, according to Sophos.

"Cyber-criminals have begun to notice consumers' growing attraction to Apple Macs during the past year," said Mike Haro, senior security analyst at Sophos.

"This trend has led to a number of viruses and malware created by hackers for the purpose of attacking consumers who purchase Mac computers.

"Mac users need to be aware that, while the threats that exist right now are few in number, they still need to take adequate measures to protect themselves. "

Sophos top 10 list of malware found on the web in 2007:

1. Mal/Iframe 53.3 %
2. Mal/ObfJS 9.8 %
3. Troj/Decdec 6.6 %
4. Troj/Psyme 6.2 %
5. Troj/Fujif 5.8 %
6. JS/EncIFra 3.9 %
7. Troj/Ifradv 2.4 %
8. Mal/Packer 1.2 %
9. Troj/Unif 1.0 %
10. VBS/Redlof 0.8 %
Others 9.0 %