Attacks exploiting an Adobe Reader zero-day vulnerability appear to have targeted defense contractors and other organizations, according to security researchers.

Adobe issued a security advisory on Dec. 6 warning Adobe Reader and Acrobat users of a critical vulnerability in how the programs accessed PDF files. The flaw was also being exploited in the wild against Adobe Reader 9.x users on Windows, Adobe said.

Symantec researchers found that attack emails with malicious PDF files that exploited the flaw were sent to telecommunications and chemical companies as well as defense contractors, Joshua Talbot, security intelligence manager of Symantec Security Response, told eWEEK.

The emails had been spoofed to look like they were sent from agencies and organizations that were familiar to the recipients, he said. Symantec security researchers found attack emails from Nov. 1 and Nov. 5 that exploited the vulnerability, Stephen Doherty, a security response engineer at Symantec, wrote on the Symantec Security Response blog Dec. 7.

Attackers used "social engineering to trick users into opening the file," Talbot said.

In a separate analysis, independent security researcher Brandon Dixon found a malicious PDF file masquerading as an employee-satisfaction survey for ManTech, a defense contractor affiliated with Lockheed Martin, Dixon wrote on 9B+ blog Dec. 7. The file was found in PDF X-Ray, a project run by Dixon to capture and detect malicious PDF files circulating on the Internet.

Lockheed Martin and the Defense Security Information Exchange were credited for bringing the vulnerability to Adobe's attention, according to the security advisory. The DSIE is a group of major defense contractors that are part of the Defense Industrial Base and share information about computer attacks with each other. DIB members include Boeing, General Dynamics, Lockheed Martin, Northrup Grumman, Pratt & Whitney and Raytheon.

The attackers were sophisticated, customizing the attack for each victim, as they crafted different PDF files and attack emails to specifically target each organization, Talbot said. "Someone in the communications industry is likely to receive a different email and PDF file than someone in a manufacturing company would," he said.

Even though the PDF files were different, both Symantec and Dixon's analysis showed that when the files were opened in Reader 9.4.6, the vulnerability was exploited to download and infect computers with malware Symantec identified as Backdoor.Sykipot. The file contained JavaScript to check the operating system and Reader's version number before executing the malicious code, Dixon said.

The attachment found by Symantec claimed to be an updated contract guide for contractors for fiscal year 2012, according to the screenshot on the Symantec blog. "The new guide contains update information of ___ policy on contract award process," the email said. The targeted emails appear to have included the name of the organization the contractor would be affiliated with.

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