Attackers Use Steganography to Obfuscate PDF Exploits

[silversurfer]

A recently discovered PDF exploit used steganography to hide malicious JavaScript code in images embedded in PDF files, according to exploit analysis firm EdgeSpot.

Steganography is a method of hiding information within files, and has been long used by cybercriminals in malicious attacks. The powerful exploit obfuscation technique allows threat actors to generate PDF documents that can bypass the detection of almost all anti-virus engines, EdgeSpot's researchers say. 

The analyzed sample was initially submitted to VirusTotal in October 2017, but only one anti-virus engine was detecting it as an exploit last week, EdgeSpot says. The detection rate didn’t improve by much by the time the researchers completed their investigation.

The sample included two layers of obfuscation, one abusing two methods to read and execute the JavaScript hidden as "content,” and the other leveraging steganography to hide the code in stream-119. 

Source: https://www.securityweek.com/attackers-u...f-exploits

[Deep900]

Unfortunately this type of obfuscation reduces the possibility of a security software to detect malicious PDF files.