Emotet brought down the entire network of a targeted organization by overheating all of its connected computers.

Microsoft’s Detection and Response Team (DART) observed that the Emotet attack began at “Fabrikam,” a pseudonym for the affected organization, when malicious actors targeted one of its employees with a phishing email. Once the recipient opened the attachment, the file informed them that it would open in cmd.exe format and communicate with the internet. Consent by the recipient allowed the file to steal the employee’s credentials and exfiltrate them to the attackers’ server.

Three days after this initial compromise, the campaign implemented its second stage by using the compromised employee’s email account to target other Fabrikam workers and external contacts with phishing emails. This stage enabled the operation to drop its Emotet payload on as many computers as possible. Just a few days after that, Emotet succeeded in maxing out the central processing unit (CPU) of all infected workstations, thereby freezing their machines. In so doing, the malware effectively took down the network and halted all IT operations at Fabrikam.

Ushering in the 2020s With Emotet

Emotet has begun the new decade with a bang. In early January, Cisco Talos revealed that it had witnessed a surge of activity in which the malware targeted the .mil and .gov top-level domains (TLDs). Less than a month later, IBM X-Force identified a campaign in which the threat leveraged tailored spam messages to target users in Japan. Also in February, Binary Defense disclosed a new variant of the malware that abused the wlanAPI interface to spread over a local area network (LAN).

How to Defend Against a Phishing Attack

Security professionals can help their organizations defend against an Emotet-laden phishing attack by using ongoing phishing simulations. Doing so will help teams evaluate their workforce’s familiarity with and preparedness against email attacks. Additionally, infosec personnel should leverage a least privilege model to limit the number of employees who can access high-value systems and data.