A phishing campaign has been identified that uses purchase order-related lures and Excel file attachments to deliver the Remcos RAT, a commercially available malware variant that gives threat actors remote access to an infected device. The malware allows the threat actor to log keystrokes, record audio via the microphone, and take screenshots and provides a foothold allowing an extensive compromise. Infection with the Remcos RAT invariably involves data theft and could lead to a ransomware attack and extortion.
Businesses with antivirus software installed are unlikely to be protected. While antivirus software is effective at detecting and neutralizing malware, the Remcos RAT is poorly detected as it is fileless malware that runs in memory and does not install files on the disk. The campaign, detected by researchers at FortiGuard Labs, targets Windows users and starts with a phishing email with an encrypted Excel attachment. The emails purport to be a purchase order and include a malicious Excel file attachment. The Excel file uses OLE objects to exploit an old vulnerability in Office, tracked as CVE-2017-0199. Successful exploitation of the vulnerability will see an HTML Application (HTA) file downloaded, which is launched using mshta.exe. The file is heavily obfuscated to evade security solutions, and its function is to download and execute a binary, which uses process hollowing to download and run the Remcos RAT in the memory.
The Remcos RAT is used to enumerate and terminate processes, execute commands, capture sensitive data, and download additional malware payloads. Since the Remcos RAT runs in the memory, it will not survive a reboot. To achieve persistence, it runs the registry editor (reg.exe) to edit the Windows Registry to add a new auto-run item to ensure it is launched after each reboot.
Since the initial contact is made via email, an advanced email security solution with email sandboxing and AI- and machine learning capabilities should ensure the email is identified as malicious and blocked to prevent delivery. Should the email be delivered and the attachment opened, end users are informed that the document is protected. They are presented with a blurred version of the Excel file and are told they need to enable editing to view the content – a red flag that should be identified by security-aware employees. If that red flag is missed, enabling content will trigger the exploitation of the vulnerability that ultimately delivers the Remcos RAT. Businesses with an advanced DNS-based web filter will have another layer of protection, as the URLs hosting the malicious files should be blocked.
TitanHQ offers cutting-edge cybersecurity solutions that provide exceptional protection against phishing, BEC, and malware attacks, blocking the initial emails and connections to malicious websites to prevent end users from viewing malicious emails (SpamTitan) and preventing malicious file downloads from the Internet (WebTitan). In November 2024 tests by Virus Bulletin, TitanHQ’s SpamTitan Solution had a 100% phishing and malware block rate. TitanHQ also provides a comprehensive security awareness training platform (SafeTitan) to teach cybersecurity best practices and keep employees aware of the latest threats. The platform also incorporates a phishing simulator for reinforcing training. Give the TitanHQ team a call today for more information on TitanHQ solutions and how they can improve your defenses against email, web, SMS, and voice-based threats at your business.