Researchers from Proofpoint have discovered a new remote access Trojan (RAT) named Parasite HTTP that implements a broad range of evasion techniques. 

The Parasite HTTP RAT has a modular architecture that allows authors to easily add new features.  The malware includes sandbox detection, anti-debugging, anti-emulation, and other defense mechanisms. 

“Proofpoint researchers recently discovered a new remote access Trojan (RAT) available for sale on underground markets.  The RAT, dubbed Parasite HTTP, is especially notable for the extensive array of techniques it incorporates for sandbox detection, anti-debugging, anti-emulation, and other protections.”  reads the analysis published by Proofpoint. 

“The malware is also modular in nature, allowing actors to add new capabilities as they become available or download additional modules post infection.” 

The Parasite HTTP RAT leverages string obfuscation and a sleep routine to delay execution and check for sandboxes or emulate environments.  It first checks if an exception handler has run, then it checks whether between 900ms and two seconds elapsed in response to the routine’s 1-second sleep split into 10ms increments. 

“Parasite HTTP contains an impressive collection of obfuscation and sandbox- and research environment-evasion techniques,” states Proofpoint

In presence of a sandbox, the RAT halts the execution and attempts to make hard the forensic investigations. 

“When Parasite HTTP actually does detect a sandbox, it attempts to hide this fact from any observers.  It does not simply exit or throw an error, instead making it difficult for researchers to determine why the malware did not run properly and crashed. ”  continues the analysis. 

Experts observed the malware using code from a public repository for sandbox detection. 

The Parasite HTTP RAT is being advertised on an underground forum.  Researchers already spotted the threat in attacks in the wild. 

The malware was involved in a small email campaign targeting organizations primarily in the information technology, healthcare, and retail industries. 

The phishing emails used weaponized Microsoft Word attachments with macros that act as a downloader for the RAT

The Parasite HTTP RAT is written in C programming language.  The author claims it has a small size (49kb) and has he no dependencies. 

It also implements plugin support and dynamic API calls support. 

Communication with the command and control (C&C) is encrypted, the author also offers a series of plugins for the malware, including User management, Browser password recovery, FTP password recovery, IM password recovery, Email password recovery, Windows license keys recovery, Hidden VNC, and Reverse Socks5 proxy. 

It is interesting to note that the malware involves a rare process injection technique.  On Windows 7 and newer versions, the malware resolves critical APIs to create registry entries. 

The experts highlighted that the Parasite HTTP RAT includes an obfuscated check for debugger breakpoints it also removes hooks on a series of DLLs to complicate the work of malware experts while investigating the threat. 

“Threat actors and malware authors continuously innovate in their efforts to evade defenses and improve infection rates.  Parasite HTTP provides numerous examples of state-of-the-art techniques used to avoid detection in sandboxes and via automated anti-malware systems.  For consumers, organizations, and defenders, this represents the latest escalation in an ongoing malware arms race that extends even to commodity malware,” Proofpoint concludes. 

Pierluigi Paganini

( Security Affairs – Parasite HTTP RAT, malware)

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