Security Experts:

New Variant of the Houdini Worm Emerges

A new variant of the well-known Houdini Worm has been spotted in phishing attacks earlier this month, Cofense’s security researchers report. 

Named WSH Remote Access Tool (RAT) by its author, the threat was released on June 2 and was spotted in a phishing campaign soon after. The email attachment contained an MHT file with a href link that directed victims to a .zip archive containing a version of the malware. 

The Houdini Worm (HWorm) has been around since at least 2013 and is best known for its bot and RAT capabilities. The newly discovered iteration represents a JavaScript (JS) port of HWorm’s original Visual Basic codebase. 

WSH, Cofense explains, could be a reference to the legitimate Windows Script Host tool, an application designed to execute scripts on Windows machines.

When run, WSH RAT behaves in the same way as HWorm, down to the use of mangled Base64 encoded data, and also features the same configuration structure. In fact, Cofense reveals, WSH RAT’s configuration is an exact copy of HWorm’s, as it even features the same names for default variables.

The URL structure used for command and control (C&C) communication is also identical to that employed by Hworm. Changes include the prepending of the id “WSHRAT” to the User-Agent string and the use of “|” as delimiter, compared to “<|>”.

The security researchers noticed that, after the initial call to the C&C, the RAT started calling to another URL for three separate payloads, served in the form of .tar.gz files, but which are in fact PE32 executables. 

The payloads, all three of which are from third-parties, are a keylogger, a mail credential viewer, and a browser credential viewer. 

WSH RAT is currently being offered as a subscription, at $50 per month. The malware operators are actively marketing the malware as compatible with all Windows XP to Windows 10 releases, featuring automatic startup methods, and various remote access, evasion, and stealing capabilities. 

They claim the threat can steal passwords from Firefox, Chrome, Internet Explorer, Edge, Opera, Outlook and Thunderbird, that it can upload/download and execute files, browse for files on the system, execute remote scripts and commands, disable User Account Control (UAC) and anti-virus products, view and kill processes, and restart or shutdown the PC.

“This re-hash of Hworm proves that threat operators are willing to re-use techniques that still work in today’s IT environment,” Cofense’s security researchers conclude. 

Related: Houdini Worm Gets Posted to Paste Sites

Related: Russian Hackers Use RATs to Target Financial Entities

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