Apple ships removal tool for Mac-menacing malware

Apple has updated its Mac operating system to protect against a malicious application that has been hoodwinked untold numbers of users by masquerading as legitimate security software that warns they have serious infections on their machines.

Apple issued Security Update 2011-003 on Tuesday to update Mac OS X to detect for MacDefender, one of several trojans that gets installed through an elaborate ruse that's become almost a rite of passage for owners of machines running Microsoft Windows. Those behind the scareware hook their victims by presenting them with web images that depict an antivirus scan taking place on their machines. The images falsely claim users have serious malware infections and urge them to download and install the antivirus package. Those who fall for the scam are then infected.

A ZDNet blogger recently counted 200 separate discussion threads on discussions.apple.com in which users complained of infections that caused their Macs to behave erratically. Apple had instructed members of its support team to withhold any confirmation that a customer's Mac has been infected with malware or to assist in removing malicious programs, the blogger, Ed Bott, had said.

Apple's malware protection debuted in a Mac OS X beta version in 2009 with signatures for just two Mac trojans. It was updated in April 2010 and in March of this year for the HellRTS and OSX.OpinionSpy trojans, respectively.

The malware detection feature monitors software downloaded by a limited number of applications, such as Safari, iChat, and Mail, and warns when the software includes one of the five malicious titles.

“Security Update 2011-003 provides additional protection by checking for the MacDefender malware and its known variants,” an Apple advisory stated. “If MacDefender malware is found, the system will quit this malware, delete any persistent files, and correct any modifications made to configuration or login files.”

Once MacDefender has been identified and removed, a message warning of the attempted attack will be displayed the next time a user logs into an administrator account. The signature is designed to detect known variants of MacDefender. That means it should flag a variant known as MacGuard, which exploits default Mac settings to install itself without requiring a user to enter an administrative password.

Once the security update is installed, it will check for updates to the malware list each day. The addition of daily malware checks is perhaps Apple's biggest admission to date that Macs aren't immune from the types of attacks that have dogged Windows users for years. ®