After exploiting Reader or Acrobat, the attack code installs -- or drops -- a payload file, which is a DLL file disguised as a "language bar addin." The malicious file then goes to sleep to help disguise the infection. Interestingly, FireEye said the malware is also designed to not do anything that a real language bar plug-in wouldn't do, and includes techniques designed to fool sandbox defenses that aim to spot and block malicious code.
According to Trend Micro, the malware used in the attack includes DLL files designed to run on 64-bit machines. "The people behind this threat may have included this 64-bit malware in an attempt to evade detection by anti-malware programs," according to a blog post from the company.
Trend Micro said that in the attack samples it gathered, a successful exploit results in a Trojan injector DLL file being dropped, as well as a non-malicious file named Visaform Turkey.pdf being copied onto the system, which is likely designed to hoodwink users into not realizing they've just executed a malicious file.
Security researcher and regular Metasploit contributor Eric Romang reported Wednesday that Visaform Turkey.pdf was first submitted Monday and then Tuesday to VirusTotal, where it was identified as being a malicious file that had been created just 10 days ago. Meanwhile, a command-and-control server tied to the attacks was anonymously submitted to jsunpack on Wednesday.
Those clues aside, security researchers have yet to detail, or perhaps identify, the targets of the malicious PDF attack or what types of data may have been targeted by the attackers.
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