A virus attacking Mac computers known as Tsunami Trojan has been discovered and early speculation suggests that it may be a DDoS attack tool, used to bring down websites.
The Trojan is thought to have been created by modifying an earlier virus known as Kaiten, which could 'phone home' from infected machines for further instructions.
Security firm Sophos has suggested that Tsunami Trojan could be used to rally computers together and force them to perform a DDoS (distributed denial-of-service) attack, which can have the power to make websites crash under heavy load.
DDoS attacks work by commanding many computers to all access the same website at once; the website's servers cannot cope with the extra load and the site goes down.
Sophos has said: "[the Trojan] can be given a variety of different instructions and can be used to remotely access n affected computer.
"The big question, of course, is how would this code find itself on your Mac in the first place? It could be that a malicious hacker plants it there, to access your computer remotely and launch DDoS attacks, or it may even be that you have volunteered your Mac to participate in an organised attack on a website."
Sophos warns that participating in a DDoS attack is illegal and that by letting the Trojan into a Mac, the owner has "effectively put control of your Mac into someone else's hands."
There has historically been very little for Mac users to worry about with regard to viruses and malware, but Tsunami Trojan has the potential to cause harm not only to the user, but also whatever company whose website falls victim to the possible DDoS attack.