Apple Snow Leopard Used as Lure for Trojan

Trend Micro finds a malware campaign that ropes in victims by offering free copies of Mac OS X 10.6, aka Snow Leopard. What users really get is a DNS-changer Trojan.

Apple plans to release Mac OS X 10.6, aka Snow Leopard, on Aug. 28, and cyber-criminals have taken notice.

A number of rogue sites have popped up offering free copies of the latest version of Apple's operating system. Researchers at Trend Micro are reporting that accessing these malicious sites lands users with a DNS (Domain Name System)-changer Trojan detected as OSX.JAHLAV.K.

"Once executed, OSX_JAHLAV.K decrypts codes, which include a script that downloads other malicious scripts," blogged Trend Micro researcher Bernadette Irinco. "The said script then alters the DNS configuration and includes two additional IP addresses in its DNS server. Users are thus possibly redirected to phishing sites and other fraudulent sites. In fact, some of these bogus sites are reportedly hosting FAKEAV (rogue anti-virus) variants and components."

This is far from the first time attackers have sought to exploit interest in popular software upgrades. Similar tactics were used to take advantage of interest in Microsoft Windows 7 earlier in 2009. By infecting pirated copies of the operating system with a Trojan, attackers sought to build a botnet of compromised computers.

According to security company Damballa, more than 27,000 copies of the malicious Windows 7 Release Candidate had been installed on computers before the company took down the botnet's command and control May 10.

In the case of the Mac Trojan, the malware is a MAC OS X mountable .DMG (Disk Image file). The script creates a cron job that enables the malware to execute every 5 minutes. It also features a chain of other encrypted codes, including the Perl script that attempts to download and execute another malicious script. Once installation is finished, files are added into the system.

Apple has sought to enhance malware protection in Snow Leopard, adding a new warning if malware is detected in files downloaded via Safari, iChat and a handful of other applications.

Trend Micro advises users to only get the Snow Leopard update directly from the Apple Website.