Shortly after it was discovered by security researchers, a rogue network linking Apple computers through a Mac Trojan had its nerve center shut down.
"The command and control server is down," Lysa Myers, a senior security analyst with Mac antivirus softwarea maker Intego, said in an interview. "We talked to the ISP yesterday and had it shut down."
Myers wrote in a blog post on Tuesday that Intego's virus scanning program discovered the Mac Trojan, which creates a backdoor in an infected machine.
The Trojan resembles malware used in recent months to attack activist websites, although it doesn't appear to be tied to the usual suspects behind those attacks.
"There have been a lot of Trojans targeting activists, journalists -- people vocal against governments," Myers explained. "This is continuing that trend."
"It doesn't seem to be made by an existing group, but it's the same idea," she added.
Without a command and control server to manipulate it, the threat level by the Trojan is low at this point.
The Trojan is disguised as an icon of a couple kissing. It has a filename that looks like a photo file from a digital camera -- DSC00117 -- but that's because the extension that would reveal the file as an executable -- .app -- is hidden.
When the icon is clicked, the Trojan installs itself on its target, carefully hiding itself from the OS X dock and Cmd-Tab shortcut, and installs a backdoor to the system. It also opens an image file in the OS X Preview app, so a victim believes they're just opening an image file.
Once it's cooking, the Trojan connects to its command and control server -- something it's not doing anymore -- to receive commands. It receives instructions to collect a variety of information about the infected system and attempts to download an image displaying the logo of the Syrian Electronic Army.
How the Trojan gets on systems in the first place is still a mystery. Some typical attack vectors are watering hole attacks, spearphishing via URL or app attacks via SQL injection or cross-site scripting.
"Web-based attacks are the most viable against Safari as all Apple devices are inherently dependent on their browsers interface with the cloud computing environment of today," said Tom Kellermann, Vice President of Cyber Security for Trend Micro.
In broad terms, Mac attacks fall into two categories. "It seems like it's either a Java exploit or there's some element of social engineering to run them," Myers said.
She added that Mac malware appears in spurts. "It's not like Windows where you can have hundreds of thousands of programs in a day," Myers said. "You get some here and there."
"We seem to be getting a spurt of backdoor Trojans now," she added.
Apple's popular image of being immune from malware has fired up hacker interest in the platform in recent times, Kellermann said.
"Every hacker is fully aware that Apple users are the wealthiest, as well as believing the Apple mythology that they are not vulnerable to malware," he said. "Thus they make the perfect sheep for the slaughter."
"I believe the Mac malware marketplace is burgeoning with not only data stealing code but code which will leverage proximity attacks," he added.