Healthcare providers are being targeted by cybercriminals using COVID-19 themed phishing emails, with the campaigns showing no sign of letting up. The volume of attacks has prompted the U.S. Federal Bureau of Investigation (FBI) to issue a further warning to healthcare providers urging them to take steps to protect their networks and block the attacks.

The first major COVID-19 themed phishing attacks targeting healthcare providers started to be detected by around March 18, 2020. The attacks have grown over the following weeks and the lures have diversified.

Campaigns have been conducted targeting at-home healthcare employees who are providing telehealth services to patients, and there has been an increase in business email compromise scams. The latter see vendors impersonated and requests sent for early or out-of-band payments due to difficulties that are being experienced due to COVID-19.

The phishing attacks are being conducted to obtain login credentials and to spread malware, both of which are used to gain a foothold in healthcare networks to allow follow-on system exploitation, persistence, and the exfiltration of sensitive data.

The malware being distributed in these campaigns is highly varied and includes information stealers such as Lokibot, backdoors, and Trojans such as Trickbot. Microsoft has recently reported that Trickbot accounts for the majority of COVID-19 phishing emails targeting Office 365 users, with a campaign last week involving hundreds of different, unique macro-laced documents. In addition to being a dangerous malware variant in its own right, Trickbot also downloads other malicious payloads, including RYUK ransomware.

A diverse range of malware is delivered by a similarly diverse range of email attachments and malicious scripts. Microsoft Word documents containing malicious macros are commonly used, as are 7-zip compressed files, Microsoft executables, and JavaScript and Visual Basic scripts. The emails are being sent from a combination of domestic and international IP addresses.

While the number of COVID-19 themed phishing emails has been increasing, the overall volume of phishing emails has not increased by a major amount. What is happening is threat actors are changing their lures and are now using COVID-19 lures as they are more likely to be opened.

The campaigns can be highly convincing. The lures and requests are plausible, many of the emails are well written, and authorities on COVID-19 such as the Centers for Disease Control and Prevention, the HHS’ Centers for Medicare and Medicaid Services, and the World Health Organization have been spoofed. Oftentimes the emails are sent from a known individual and trusted contact, which makes it more likely that the email attachment will be opened.

The advice offered from the FBI is to follow cybersecurity best practices such as never opening unsolicited email attachments, regardless of who appears to have sent the email. Ensuring software is kept up to date and patches are applied promptly is also important, as is turning off automatic email attachment downloads. The FBI has also recommended filtering out certain types of attachments through email security software, something that is easy to do with SpamTitan.

The FBI has stressed the importance of not opening email attachments, even if antivirus software says that the file is clean. As the Trickbot campaign shows, new variants of malicious documents and scripts are being created at an incredible rate, and signature-based detection methods cannot keep up. This is another area where SpamTitan can help. In addition to using dual antivirus engines to identify known malware variants faster, SpamTitan includes sandboxing to identify and block zero-day malware threats that have yet to have their signatures added to antivirus software virus definitions lists.

Training is important to teach healthcare employees cybersecurity best practices to help them identify phishing emails, but it is also important to ensure that your technical controls are capable of blocking these threats. For more information on the latter, give the TitanHQ team a call today.