Cyber Criminals now using new Stenography technique to distribute a powerful Obfuscated PDF exploit in order to compromise the targets and evade the detection.
Malicious hackers are always finding new techniques to exploit the vulnerabilities and compromising victims machine without more user interaction to increase the success ratio of the attack.
Steganography is the technique of hiding secret data and malicious data within an ordinary, non-secret, file or message in order to avoid detection; the secret data is then extracted at its destination.
An identified sample was uploaded into Virustotal on 2017-10-10, with a filename “oral-b
Analyzing the PDF Exploit
Researchers discovered that there are two different layer of obfuscation has been used in this PDF exploit.
The First layer using two different functions “this.getPageNumWords()” and “this.getPageNthWord()” to Extract PDF Pages Based on hidden Content.
Based on the API references, these two APIs, working together, are to read the stream of an image named as “icon” stored in the PDF file.
The icon stream named “icon” in the object-131 could be saved as a “jpg” file and viewed in image viewer without
There is no malicious data found inside of the “icon”file since the file is heavily obfuscated.
In this case, attackers copied the open source steganography technique called “steganography.js” to successfully perform this attack.
“We believe the person behind the PDF samples made their innovation as they successfully leveraged the technique in PDF format. We could not find any information mentioning such technique in PDF exploits before, so we believe this is the first time that the “steganography” technique is used to hide PDF exploits”., Researchers said.