macOS RAT Uses 0-Day for Root Access

A new remote access tool (RAT) targeting macOS and believed to be using an unpatched 0-day vulnerability to gain root access on target machines, is currently being advertised on underground markets.

Dubbed Proton, the RAT was found on a closed Russian cybercrime message board, being offered by its author “in one of the leading underground cybercrime markets,” Sixgill researchers report. The Trojan is currently offered at 2 Bitcoins (around $2,500) for single installations, but an unlimited installations option is also available, at 40 Bitcoin.

According to the author, the tool was written in native Objective C and is fully undetectable by existing anti-virus programs for macOS. Objective C, the security researchers say, offers the great advantage that the malware doesn’t require dependencies.

Advertised as “a professional FUD surveillance and control solution” and packing root-access privileges and features, the tool allows an attacker to take full control of the victim’s machine. The malware can execute any bash command under root, monitor keystrokes, upload/download files to/from the victim’s machine, grab screenshots or webcam captures, get updates, and also send notifications to the attacker.

The Trojan also enables the attacker to connect via SSH/VNC to the target machine, and can even present a custom native window requesting information such as a credit-card, driver’s license and more. Further, the tool also packs iCloud access capability, even when two-factor authentication is enabled.

The malware can deliver these features because it “is shipped with genuine Apple code-signing signatures,” Sixgill researchers explain. The author might have tricked Apple’s filtration process for third-party software developers, either by registering to Apple’s developer program under a false ID, or by leveraging stolen developer credentials, which allowed them to get the necessary certificates.

Of higher concern would be the use of a previously unpatched 0-day vulnerability to gain root access. If such a vulnerability indeed exists and Proton’s author is in its possession, others might be aware of it and even exploit it as well.

For distribution, Proton’s operators would simply need to masquerade the Trojan as a genuine application, with a custom icon and name, and then trick the victim into downloading and installing it.

The RAT is being sold through a dedicated website that also includes some promotional material related to the malware, along with a login system, the researchers say. Proton’s author advertises the tool under the premise of legitimate use, and even uploaded a short video demonstrating the installation process to YouTube.

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Ionut Arghire is an international correspondent for SecurityWeek.

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