Long the beneficiary of security through obscurity, Macs may have become popular enough to bring malware writers over to the platform.
Intego, a company that makes Mac security software, on Tuesday issued a warning that malicious Trojan software capable of compromising computers running Mac OS X has been found on several pornography sites. The Trojan, OSX.RSPlug.A, represents one of the relatively few Mac exploits to be spotted in the wild.
Users who click on images hoping to launch videos at the sites in question see a message that claims the user's QuickTime Player media software needs to be updated. Depending on how the user's computer is configured, the Trojan may download and launch an installer automatically. Upon authorization with the user's name and password, the Trojan program will be installed with root access (assuming the user is running an administrator account, as many do, contrary to recommended practice).
"This Trojan horse, a form of DNSChanger, uses a sophisticated method, via the scutil command, to change the Mac's DNS server (the server that is used to look up the correspondences between domain names and IP addresses for web sites and other Internet services)," Intego said in an online advisory. "When this new, malicious, DNS server is active, it hijacks some Web requests, leading users to phishing web sites (for sites such as eBay, PayPal and some banks), or simply to web pages displaying ads for other pornographic web sites. In the first case, users may think they are on legitimate sites and enter a user name and password, a credit card, or an account number, which will then be hijacked. In the latter case, it seems that this is being done solely to generate ad revenue."
Intego notes that users of OS X 10.4 (Tiger) cannot see the DNS changes but that users of Apple's new OS X 10.5 (Leopard) can, in the Advanced Network preferences window.
The Trojan also installs a root crontab -- a program that runs periodically -- that checks every minute to make sure the malicious DNS server is still active, Intego said.
Intego's October 31, 2007 virus definitions protect against the exploit. Avoiding software distributed by porn sites might help too.