Picking Apart Remcos Botnet-In-A-Box
Cisco Talos has recently observed multiple campaigns using the Remcos remote access tool (RAT) that is offered for sale by a company called Breaking Security. While the company says it will only sell the software for legitimate uses as described in comments in response to the article here and will revoke the licenses for users not following their EULA, the sale of the RAT gives attackers everything they need to establish and run a potentially illegal botnet.
Remcos’ prices per license range from €58 to €389. Breaking Security also offers customers the ability to pay for the RAT using a variety of digital currencies. This RAT can be used to fully control and monitor any Windows operating system, from Windows XP and all versions thereafter, including server editions.
In addition to Remcos, Breaking Security is also offering Octopus Protector, a cryptor designed to allow malicious software to bypass detection by anti-malware products by encrypting the software on the disk. A YouTube video available on the Breaking Security channel demonstrates the tool’s ability to facilitate the bypass of several antivirus protections. Additional products offered by this company include a keylogger, which can be used to record and send the keystrokes made on an infected system, a mass mailer that can be used to send large volumes of spam emails, and a DynDNS service that can be leveraged for post-compromise command and control (C2) communications. These tools, when combined with Remcos provide all the tools and infrastructure needed to build and maintain a botnet.
Within Cisco’s Advanced Malware Protection (AMP) telemetry, we have observed several instances of attempts to install this RAT on various endpoints. As described below, we have also seen multiple malware campaigns distributing Remcos, with many of these campaigns using different methods to avoid detection. To help people who became victims of a harmful use of Remcos, Talos is providing a decoder script that can extract the C2 server addresses and other information from the Remcos binary. Please see the Technical Details section below for more information.