The next version of Apple's OS X, which is due out Friday, may bundle antivirus capabilities.
The company published a screenshot which it said was of the security feature detecting a Trojan in a download, made via Apple's Safari Web browser.
Intego pointed out that the most recent Mac adverts compare Mac security favorably to PCs. However, security experts have historically been divided over the relative security of Microsoft and Apple code, while some point out that any comparison is further complicated by the differing market penetration of Macs and PCs.
Tom Espiner of ZDNet UK reported from London.