Pierluigi Paganini December 09, 2017

According to Fortinet, crooks are abusing the Orcus RAT to target Bitcoin investors with their malicious software.

Crooks always follow money trying to catch any opportunity, such as the recent spike in the value of Bitcoin. According to the experts from Fortinet, cybercriminals are abusing the Orcus RAT to target Bitcoin investors with their malicious software.

The attack chain starts with phishing messages advertising a new Bitcoin trading bot application called “Gunbot” developed by GuntherLab.

The malicious emails come with a .ZIP attachment that includes a simple VB script that acts as a downloader, the script downloads a binary masquerading as a JPEG image file.

The downloaded binary is a Trojanized version of an open source inventory system tool named TTJ-Inventory System. The malicious code uses a hardcoded key to decrypt encoded code into another .NET PE executable that is loaded and executed directly to memory.

The malicious code verifies that it is the only instance running on the infected machine checking the presence of a mutex named “dgonfUsV”.

This binary contains three embedded PE executables in its resource, including the actual Orcus RAT server.

The three embedded PE executables are:

• M – Orcus RAT server
• PkawjfiajsVIOefjsakoekAOEFKasoefjsa – persistence watchdog
• R – RunPE module

Experts discovered a RunPE module can execute modules without writing them to the system, and can also execute them under legitimate executables by running applications in suspended mode and then replacing the process’ memory with the malicious code.

“The RunPE module is not only able to execute other modules without writing their physical files in the system, but also to execute them under legitimate executables. This is usually done by executing an application in suspended mode, and then replacing the new process’ memory with the malicious code before resuming. It’s a common stealth technique. In this case, it uses components of the Microsoft .NET framework, MSBuild.exe and RegAsm.exe, as shells to hide their malicious processes.” reads the analysis published by Fortinet.

“The module from the PkawjfiajsVIOefjsakoekAOEFKasoefjsa resource acts as a watchdog to keep the malware running by repeatedly executing it unless the client decides to stop it by dropping ”stop.txt” in its directory.”

The Orcus RAT is around since early 2016, it implements common RAT features and it is also able to load plugins and execute C# and VB.net code on the remote machine in real-time.

“Orcus has been advertised as a Remote Administration Tool (RAT) since early 2016. It has all the features that would be expected from a RAT and probably more.” continues the analysis.

“The long list of the commands is documented on their website. But what separates Orcus from the others is its capability to load custom plugins developed by users, as well as plugins that are readily available from the Orcus repository. In addition to that, users can also execute C# and VB.net code on the remote machine in real-time.”

The Orcus RAT is a powerful spyware, it can disable the light indicator on webcams to spy on the victims without raising suspicion.

The malware can also implement a watchdog that restarts the server component and If the someone tries to kill its process it can trigger a Blue Screen of Death (BSOD).

Orcus also includes a plugin that can be used to power Distributed Denial of Service (DDoS) attacks.

“It is obvious that the malware download site https://bltcointalk.com is trying to imitate the bitcoin forum bitcointalk.org. When accessed, the website is just an open directory containing the previously mentioned as well as an archive with the filename. Unfortunately, in the middle of writing this article, the contents of the website changed before we could download an updated copy.” state the analysis published by Fortinet.

The researchers observed several websites that attempt to clone legitimate domains by changing a single letter in the URL, the overall domains belong to a pool used by crooks for different campaigns.

“It was no surprise, therefore, that we found other domains that use similar domain names with replaced letters. When accessed, most of the sites display the “We’ll be back soon!”message, which is the same page that is displayed when “index.phptopic=3D1715214.0/” is accessed in “bltcointalk.com”.” states the analysis.

“In our investigation of Orcus RAT, we have again proven again that its capabilities go beyond the scope of a harmless administration tool. Regardless of the developer’s claim and defense, the reality is that the application is being used in cybercrime campaigns.” 

Technical details, including IoC are available in the blog post published by Fortinet.

Pierluigi Paganini

(Security Affairs – Orcus RAT, Bitcoin)

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Clarification

The previous version of the post attributed the campaign to the author of the Orcus RAT. It was my error in confusing the RAT name.

The RAT was abused by crooks and its authors are not involved in any fraudulent activity related this specific campaign.