New Mac malware poses as PDF doc

But Trojan code is crude, can't yet connect to control server, say security firms

Security firms today warned Mac users of a new Trojan horse that masquerades as a PDF document.

The malware, which was spotted by U.K.-based Sophos and Finnish antivirus vendor F-Secure, uses a technique long practiced by Windows attackers.

"This malware may be attempting to copy the technique implemented by Windows malware, which opens a PDF file containing a '.pdf.exe' extension and an accompanying PDF icon," said F-Secure today.

That practice relies on what is called the "double extension" trick: adding the characters ".pdf" to the filename to disguise an executable file.

The Mac malware uses a two-step process, composed of a Trojan "dropper" utility that downloads a second element, a Trojan "backdoor" that then connects to a remote server controlled by the attacker, using that communications channel to send information gleaned from the infected Mac and receiving additional instructions from the hacker.

Because it doesn't exploit a vulnerability in Mac OS X -- or any other software -- the malware instead must dupe users into downloading and opening the seemingly-innocuous PDF document, which is actually an executable.

Once run, the dropper downloads the second-stage backdoor and opens a Chinese-language PDF. F-Secure said that the PDF was another sleight-of-hand trick: "[The dropper component] drops a PDF file in the /tmp folder, then opens it to distract the user from noticing any other activity occurring," the company said in a description of the attack.

Both Sophos and F-Secure noted that the malware doesn't work reliably, and currently can't connect to the command-and-control (C&C) server because the latter isn't fully functional.

Mac malware is typically crude in comparison with what targets Windows PCs.

Because the C&C server is not yet operational and since it found samples of the Trojans on VirusTotal -- a free service that runs malware against a host of antivirus engines -- F-Secure speculated that the malware is still in the testing phase.

Although Apple's Mac OS X includes a bare-bones antivirus detector, it has not been updated to detect the just-noticed Trojan dropper or backdoor. Checks of several Computerworld Macs running Lion, for instance, found that Apple last updated its detector on Aug. 9.

Mac users had their biggest malware scare earlier this year, when a series of fake security programs , dubbed "scareware," were aimed at them.

Several antivirus companies, including Sophos, F-Secure and Intego, offer security software for the Mac.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer , or subscribe to Gregg's RSS feed . His e-mail address is gkeizer@ix.netcom.com .

Read more about security in Computerworld's Security Topic Center.

Join the Good Gear Guide newsletter!

Error: Please check your email address.

Tags sophosMac OSsecurityf-securesoftwareMalware and Vulnerabilitiesoperating systems

Our Back to Business guide highlights the best products for you to boost your productivity at home, on the road, at the office, or in the classroom.

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gregg Keizer

Computerworld (US)
Show Comments

Essentials

Microsoft L5V-00027 Sculpt Ergonomic Keyboard Desktop

Learn more >

Lexar® JumpDrive® S57 USB 3.0 flash drive

Learn more >

Mobile

Lexar® JumpDrive® S45 USB 3.0 flash drive 

Learn more >

Exec

Lexar® Professional 1800x microSDHC™/microSDXC™ UHS-II cards 

Learn more >

Audio-Technica ATH-ANC70 Noise Cancelling Headphones

Learn more >

Lexar® JumpDrive® C20c USB Type-C flash drive 

Learn more >

HD Pan/Tilt Wi-Fi Camera with Night Vision NC450

Learn more >

Budget

Back To Business Guide

Click for more ›

Most Popular Reviews

Latest News Articles

Resources

PCW Evaluation Team

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Aysha Strobbe

Windows 10 / HP Spectre x360

Ultimately, I think the Windows 10 environment is excellent for me as it caters for so many different uses. The inclusion of the Xbox app is also great for when you need some downtime too!

Mark Escubio

Windows 10 / Lenovo Yoga 910

For me, the Xbox Play Anywhere is a great new feature as it allows you to play your current Xbox games with higher resolutions and better graphics without forking out extra cash for another copy. Although available titles are still scarce, but I’m sure it will grow in time.

Kathy Cassidy

STYLISTIC Q702

First impression on unpacking the Q702 test unit was the solid feel and clean, minimalist styling.

Anthony Grifoni

STYLISTIC Q572

For work use, Microsoft Word and Excel programs pre-installed on the device are adequate for preparing short documents.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?