Apple's Mac OS X operating system is being targeted by backdoor Trojan malware dubbed OSX/Tsunami-A.
The malware has been identified as a Linus backdoor Trojan that embeds itself on a computer system and monitors an IRC channel for further instructions.
The Tsunami part of the name given to the malware refers to the fact that this type of code typically gathers compromised computers to flood websites with distributed denial-of-service (DDoS) attacks, said Graham Cluley, senior technology consultant at security firm Sophos.
OSX/Tsunami-A, however, is more than a simple DDoS tool as it can respond to a variety of different instructions and can be used to remotely access an affected computer, Cluley wrote in a blog post.
Cluley reminded Mac users that even though there is far less malware for Mac OS X than for Windows, that does not mean the problem is non-existent.
"We fully expect to see cybercriminals continuing to target poorly protected Mac computers in the future. If the bad guys think they can make money out of infecting and compromising Macs, they will keep trying," he said.
Sophos is updating its Mac anti-virus products, including its free anti-virus for Mac home users, to detect OSX/Tsunami-A.
"My advice to Mac users is simple: don't be a soft target, protect yourself," said Cluley.
He also cautions against volunteering to take part in an organised attack on a website.
"Not only is participating in a DDoS attack illegal, it also means that you have effectively put control of your Mac into someone else's hands," said Cluley.