Major malware campaign abuses unfixed PDF flaw

Message poses as e-mail reset instructions, plants worm that can spread via flash drive

Several security companies today warned of a major malware campaign that tries to dupe users into opening rigged PDFs that exploit an unpatched design flaw in the format.

Users who open the attack PDFs are infected with a variant of a Windows worm known as "Auraax" or "Emold," researchers said.

The malicious messages masquerade as mail from company system administrators and come with the subject heading of "setting for your mailbox are changed," said Mary Grace Gabriel, a research engineer with CA Inc.'s security group . A PDF attachment purportedly contains instructions on how to reset e-mail settings. "SMTP and POP3 servers for ... mailbox are changed. Please carefully read the attached instructions before updating settings," the message states.

In reality, the PDFs contain embedded malware and use the format's /Launch function to execute that malware on Windows PCs running the newest versions of the free Adobe Reader, Adobe's for-a-fee Acrobat and other PDF viewers, such as Foxit Reader.

The /Launch feature is not a security vulnerability per se, but actually a by-design function of the PDF specification. Earlier this month, Belgium researcher Didier Stevens demonstrated how attack PDFs could use /Launch to run malware tucked into documents.

Two weeks ago, security researchers tracked a new run by the Zeus botnet that used the /Launch flaw to infect PCs.

Adobe has previously declined to answer questions on whether in-the-wild use of /Launch in rigged PDFs would prompt the company to update Reader and Acrobat, although it has said a change to the functionality might "conceivably [be made] available during one of the regularly scheduled quarterly product updates." Brad Arkin, Adobe's head of security and privacy, has acknowledged that one possible solution would be to disable the function; currently, it's turned on by default.

After analyzing the attack PDF, other researchers found that hackers are using Stevens' tactic of modifying the warning that Reader and Acrobat display. Adobe Reader, for example, displays a message telling users to open only those files they know are safe. In the same Windows dialog box, Reader displays the filename of the file about to be launched. According to IBM Internet Security Systems researchers , hackers have modified the warning to simply read, "Click the 'open' button to view this document."

Other security researchers, including those at Paris-based CERT-Lexsi , have also reported on the e-mail bearing rogue PDF attachments. CERT-Lexsi added that the malware's command-and-control server is located in Korea.

IBM researchers said the malware launched from the rigged PDF seems to be version of Auraax or Emold worm. The worm drops a rootkit onto the compromised PC, and also tries to copy itself to all removable drives, including flash drives, to spread using the "Autorun" infection tactic made popular by 2008's Conficker worm.

Staff at IDG -- which is the parent company of Computerworld -- have received the malicious messages with attached PDF documents. Those messages can pose as ones from "customersupport@ domain name .com," "support@ domain name .com," and "admin@ domain name .com," where domain name is typically the company's name.

An Adobe spokeswoman today declined to comment on the latest attacks, and said the company was still researching the /Launch functionality in Adobe Reader and Acrobat to identify "all possible use scenarios for this particular functionality to ensure we are not breaking any common workflows for our customers." Adobe's current advice remains that users configure Reader and Acrobat to stymie such attacks, she added. Adobe has posted instructions on its Web site.

IBM's security team also recommended that users disable Windows' Autorun feature for all flash drives, and pointed them toward a Microsoft support document for instructions and updates.

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 malware and vulnerabilities in Computerworld's Malware and Vulnerabilities Knowledge Center.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags malwarepdf bug

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

Gregg Keizer

Computerworld (US)
Show Comments

Brand Post

Win pair of MOMENTUM True Wireless

Three PC World readers will be in the running to take home a pair of MOMENTUM True Wireless which are meticulously crafted with every fine listening detail considered. *T&C's Apply

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Jack Jeffries

MSI GS75

As the Maserati or BMW of laptops, it would fit perfectly in the hands of a professional needing firepower under the hood, sophistication and class on the surface, and gaming prowess (sports mode if you will) in between.

Taylor Carr

MSI PS63

The MSI PS63 is an amazing laptop and I would definitely consider buying one in the future.

Christopher Low

Brother RJ-4230B

This small mobile printer is exactly what I need for invoicing and other jobs such as sending fellow tradesman details or step-by-step instructions that I can easily print off from my phone or the Web.

Aysha Strobbe

Microsoft Office 365/HP Spectre x360

Microsoft Office continues to make a student’s life that little bit easier by offering reliable, easy to use, time-saving functionality, while continuing to develop new features that further enhance what is already a formidable collection of applications

Michael Hargreaves

Microsoft Office 365/Dell XPS 15 2-in-1

I’d recommend a Dell XPS 15 2-in-1 and the new Windows 10 to anyone who needs to get serious work done (before you kick back on your couch with your favourite Netflix show.)

Maryellen Rose George

Brother PT-P750W

It’s useful for office tasks as well as pragmatic labelling of equipment and storage – just don’t get too excited and label everything in sight!

Featured Content

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?