Malware News New Agent Tesla Malware Variant Using ZPAQ Compression in Email Attacks


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Aug 17, 2014
A new variant of the Agent Tesla malware has been observed delivered via a lure file with the ZPAQ compression format to harvest data from several email clients and nearly 40 web browsers.

"ZPAQ is a file compression format that offers a better compression ratio and journaling function compared to widely used formats like ZIP and RAR," G Data malware analyst Anna Lvova said in a Monday analysis. "That means that ZPAQ archives can be smaller, saving storage space and bandwidth when transferring files. However, ZPAQ has the biggest disadvantage: limited software support."
The latest attack chain begins with an email containing a ZPAQ file attachment that purports to be a PDF document, opening which extracts a bloated .NET executable that's mostly padded with zero bytes to artificially inflate the sample size to 1 GB in an effort to bypass traditional security measures.

"The main function of the unarchived .NET executable is to download a file with .wav extension and decrypt it," Lvova explained. "Using commonly used file extensions disguises the traffic as normal, making it more difficult for network security solutions to detect and prevent malicious activity."

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