SQUIRRELWAFFLE Malware

Adversaries don’t work 9-5 and neither do we. At eSentire, our 24/7 SOCs are staffed with Elite Threat Hunters and Cyber Analysts who hunt, investigate, contain and respond to threats within minutes.

We have discovered some of the most dangerous threats and nation state attacks in our space – including the Kaseya MSP breach and the more_eggs malware.

Our Security Operations Centers are supported with Threat Intelligence, Tactical Threat Response and Advanced Threat Analytics driven by our Threat Response Unit – the TRU team.

In TRU Positives, eSentire’s Threat Response Unit (TRU) provides a summary of a recent threat investigation. We outline how we responded to the confirmed threat and what recommendations we have going forward.

Here’s the latest from our TRU Team…

What did we find?

• SQUIRRELWAFFLE malware infections were identified across multiple customer environments. Although it first emerged in September 2021, it has been observed impacting our customers with increased frequency.
• Similar to Emotet, SQUIRRELWAFFLE is used as a foothold for conducting further attacks, such as the deployment of Qakbot and Cobalt Strike.
  • SQUIRRELWAFFLE leverages hijacked email threads to add malicious links to existing conversations (see XLS document in Figure 1). Enabling macros in these documents results in execution of SQUIRRELWAFFLE followed by secondary actions.
  • Secondary actions can include deployment of additional malware payloads and attack tools followed by privilege escalation and lateral movement within the network.

Figure 1 SQUIRRELWAFFLE XLS Document

How did we find it?

• eSentire’s MDR for Endpoint agent identified malicious Excel documents installing SQUIRRELWAFFLE malware and follow-on threats such as Qakbot and Cobalt Strike.
• eSentire’s MDR for Network agent identified C2 communications, such as Qakbot command and control communications and remote access tool communications.
• Our Machine Learning PowerShell classifier identified lateral movement actions.

What did we do?

• Isolated infected hosts where SQUIRRELWAFFLE payloads were identified.
• Identified and contained hosts where lateral movement occurred.

What can you learn from this TRU positive?

• The SQUIRRELWAFFLE threat specializes in malware distribution via email.
• Techniques such as email thread hijacking (replaying stolen email chains with added malicious content) have shown success in getting malware into users’ inboxes.
• If left untouched, this threat can be used as a foothold for further attacks.
• Ransomware has not been observed but remains a possibility.
  • Qakbot’s ties to ransomware have been well-documented.

Recommendations from our Threat Response Unit (TRU) Team:

• Preventing email-borne malware requires a layered defense so employ email filtering and protection measures, such as:
  • Block or quarantine email attachments such as EXEs, Password-Protected ZIPs, JavaScript, VisualBasic scripts.
  • Implement anti-spoofing measures such as DMARC and SPF.
  • Employ a Multi-Factor Authentication (MFA) solution to reduce the impact of compromised credentials.
  • Train users to identify and report suspicious emails, including from trusted contacts.
• Protect endpoints against malware by:
  • Ensuring antivirus signatures are up-to-date.
  • Using a Next-Gen AV (NGAV) or Endpoint Detection and Response (EDR) product to detect and contain threats.
  • Limiting or disabling macros across the organization. See UK's National Cyber Centre guidance on Macro Security.

Ask Yourself…

• Can you identify and contain distribution malware prior to follow-on attacks?
• Do you have the visibility across your environment to identify, contain and eradicate hands-on-keyboard threats?

If you’re not currently engaged with a Managed Detection and Response provider, we highly recommend you partner with us for security services in order to disrupt threats before they impact your business.

Want to learn more? Connect with an eSentire Security Specialist.