One of the most effective ways of getting employees to open malicious emails is to make the emails appear to have been sent internally and to use a lure related to salaries, as is the case with a recently identified campaign that is used to deliver a Remote Access Trojan called NetSupport RAT.

The campaign was first identified by researchers at Perception Point who intercepted an email that appeared to have been sent by the accounts department and purported to be a monthly salary report. The recipient is told to review the report and get back in touch with the accounts department if they have any questions or concerns about the data.  Due to the sensitive nature of the data, the salary chart is in a password-protected document, and the employee is told to enter the password provided in the email if the enable editing option is unavailable. The user is prompted to download the .docx file, enter the password, and then click enable editing, after which they need to click on the image of a printer embedded in the document. Doing so will display the user’s salary graph.

The document uses an OLE (Object Linking and Embedding) template which is a legitimate tool that allows linking to documents and other objects, in this case, a malicious script that is executed by clicking on the printer icon. This method of infection is highly effective, as the malicious payload is not contained in the document itself, so standard antivirus scans of the document will not reveal any malicious content. If the user clicks the printer icon, a ZIP archive file will be opened that includes a single Windows shortcut file, which is a PowerShell dropper that will deliver the NetSupport RAT from the specified URL and execute it, also adding a registry key for persistence.

NetSupport RAT has been developed from a legitimate remote desktop tool called NetSupport Manager which is typically used to provide remote technical support and IT assistance. The malware allows a threat actor to gain persistent remote access to an infected device, gather data from the endpoint, and run commands. While the use of OLE template manipulation is not new, this method has not previously been used to deliver the NetSupport RAT via email.

The threat actor uses encrypted documents to deliver the malware to evade email security solutions, and the emails are sent using a legitimate email marketing platform called Brevo, which allows the emails to pass standard reputation checks. This campaign is another example of how threat actors are increasing the sophistication of their phishing campaigns and how they can bypass standard email security defenses, including Microsoft’s anti-malware and anti-phishing protections for Microsoft 365 environments.

While the lure and the steps users are taken through are reasonable, there are red flags at various stages of the infection process where end users should identify the email as potentially malicious. In order for that to happen, end users should be provided with regular security awareness training. TitanHQ offers a comprehensive security awareness training platform called SafeTitan, which includes training modules to teach employees how to identify the red flags in email campaigns such as this. The platform also includes a phishing simulator, that allows these types of emails to be sent to employees to test the effectiveness of their training. If they fail a simulation, they are immediately shown where they missed the opportunity to identify the threat, with relevant training generated instantly in real time.

Sophisticated phishing attacks require sophisticated anti-phishing defenses to block these emails before they reach end users’ inboxes. While standard antivirus checks can block many malicious payloads, behavioral analysis of attachments and files is essential. TitanHQ’s cloud-based anti-spam service – SpamTitan – performs a barrage of front-end checks of messages including reputation checks and Bayesian analysis, machine-learning algorithms analyze messages for potentially malicious and phishing content, scan attachments with twin antivirus engines, and messages are sent to a sandbox for deep analysis. In the sandbox, malicious behavior can be identified allowing even sophisticated phishing emails to be blocked by the cloud spam filter.

A hosted email filter is often the best fit for businesses, although SpamTitan is available as a gateway spam filter. The TitanHQ team will be happy to listen to your requirements and suggest the best option to meet your needs. Give the team a call today to find out more about improving your email defenses against sophisticated phishing and malware distribution campaigns and how to provide more effective security awareness training.