Down the H-W0rm Hole with Houdini’s RAT

Commodity Remote Access Trojans (RATs) — which are designed, productized and sold to the casual and experienced hacker alike — put powerful remote access capabilities into the hands of criminals. RATs, such as H-W0rm, njRAT, KilerRAT, DarkComet, Netwire, XtremeRAT, JSocket/AlienSpy/Adwind and others, hold special interest for the Threat Research Team at Fidelis Cybersecurity. We’re constantly following, detecting and monitoring the lifecycle of these RATs as they appear, disappear and often reappear under a new moniker.

There have been recent reports ^{1, 2} about a new version of one such commodity RAT, H-W0rm (Hworm), and the various campaigns it is being used in. Our telemetry shows that H-W0rm is one of the most active RATs we’ve seen, with infections observed across virtually all enterprise verticals and geographies in which Fidelis Cybersecurity products are deployed.

In this blog post, the Threat Research Team at Fidelis Cybersecurity is supplementing these recent reports by providing the security community with the following:

• Technical descriptions of the payload behavior when installed on the victim machine.
• Domains observed in active infections over the past six months. We also make a larger mined dataset available through Fidelis Barncat, a malware configuration intelligence database shared at no cost with trusted third parties.
• Artifacts correlating Hworm C2 domains with njRAT, XtremeRAT and DarkComet.
• Yara rules that can be used to detect the VBS and PE versions of H-W0rm.

The following is a screenshot of the Hworm v.1.3 panel and the builder tab:

 Hworm 1.3 builder panel

Hworm 1.3 server builder window

A Worm That’s Really a RAT

It is worth clarifying that even though the malware is known as H-W0rm/Hworm, this version is not a typical worm. Specifically, it features classic Remote Access Trojan capabilities that allow the adversary to fully control the infected system. Here is rundown of some of these capabilities:

• Collect system information: hardware ID, client name/campaign code, computer name, operating system, worm/RAT version, information about AV installed, webcam presence, etc.
• File Manager: download, rename, delete, execute
• Remote Desktop capture/screenshot
• Keylogger
• Collect password filled in forms from web browsers, such as Mozilla Firefox, Google Chrome, and Opera
• Webcam
• Microphone
• Run remote application or script from disk or internet, or load it in memory via RunPE
• Update RAT from disk or internet
• Close connection
• Uninstall RAT

Let’s Go to the Videotape

A YouTube video shows an Hworm version that is referred to as version 2. The following is a screenshot from one of the windows presented in the video:

The Exploit panel, under the Builder tab, looks interesting. At the moment, it is unclear how this feature works, but its mere presence suggests the potential for creating and integrating future exploits into the malware. The following is a screenshot of the panel:

Our analysis found that one of the samples saved keystroke data into the %TEMP% directory using the filename [malware_name.dat]. In this instance, the malware was configured from the builder to be installed in the %TEMP% directory, but based on the builder settings, it can be installed in the following directories:

• %APPDATA%
• %USERPROFILE%
• %PROGRAMDATA% (Windows 7)
• %TEMP%

The malware also created the following hidden folder in the attached USB drive: $RECYCLE.BIN.

The Link to Houdini

There has been speculation in the research community ^{3, 4,5}  that “Houdini” (aka ‘Mohamed Benabdellah’) is believed to have connection with “njq8” (aka ‘Naser Al Mutairi’), the initial developer of “njRAT” and “njw0rm”.  It has further been speculated that “Houdini” is based in Algeria and “njq8” in Kuwait. It is also said that “njq8” has a connection with “Black Mafia” on the development on “Black Worm”, indicating potential collaboration between these RAT developers.

AV Information in the Network Traffic

The network traffic of some versions of the Hworm malware contain information about the antivirus tool installed in the victim system. This data indicates that some of the infected systems appeared to have been running antivirus tools like:

• Microsoft Security Essentials
• Symantec Endpoint Protection
• McAfee VirusScan Enterprise
• ESET Smart Security
• Windows Defender

Normally, those tools will detected the malware, but for some unknown reason it looks like the AV tools didn’t remove those versions of the Hworm malware running in memory. Without a copy of the specific Hworm version in the victim system and a Forensics investigation, it is difficult to confirm why those AV tools didn’t remove the sample from those victim system.

Protect Yourself

These findings are another validation of how a layered approach to secure the network enterprise is needed to protect your endpoints from these cyber threats.

In order to aid the security community with indicators of the Hworm RAT, the following is a list of C2 domains we have seen in the past six months:

From the above domains, the following one quickly stands out: “njrat2012.no-ip[dot]biz”. The last Hworm activity observed at a client site with this domain was on Oct 2016. pDNS data shows that in June 2016 this domain was associated with Xtreme RAT activity. We also found samples of njRAT v.0.7d and v.0.4.1a beaconing to this domain. The following table shows some of the C2 correlations:

To aid the security community, we’re constantly enriching Fidelis Barncat with newer Hworm configurations using our mining techniques.

The following Yara rules can also be used to detect this threat: