A new campaign is targeting people with messages that seem to come from the U.S. Department of Labor (DoL), trying to trick them into opening a DOC file, enabling macros, and eventually deploying the TrickBot malware.
Like many of today’s malicious campaigns, this new one tries to use COVID-19 as a cover to give it a sense of urgency. The use of an official government institution is a well-known tactic and, in this case, the bad actors impersonate the Department of Labor.
The email message talks about a provision called the Family and Medical Leave Act (FMLA), which allows sick employees to receive benefits when they miss work. Given the economic situation, the email aims to convince people that they need to read a document attached to the email.
An analysis from IBM X-Force of the email shows that it contains one malicious file, named “Family and Medical Leave of Act 22.04.doc.” It’s an actual DOC file but asks for the users to enable Macros when opened. When the file is closed, the attack runs scripts.
Macros are very useful in office suites, used to display dynamic content or for various automatization procedures, but they should remain off at all times. They can be used to execute scripts, allowing attackers to download malware.
And this is precisely the route taken in this case. After the user enables Macros, a file named terop.bat is downloaded and executed. But things get iffy from there, as the attackers use cURL to download a number of files from a compromised domain, only to fail. cURL is not available by default in Windows-powered machines, so the commands present in the .bat file fail.
The researchers presume the attackers are still testing deployment methods and procedures, and that’s why the download fails. But looking at the IP address and the type “Macros on close” method indicates that the malware to be eventually downloaded is Trickbot.
The Trickbot malware is adaptive and is used with different attack vectors. It initially started as a credential-harvesting threat, mostly focusing on e-banking, but it has a modular structure and allows the use of specialized plugins that lets bad actors change its purpose depending on the campaign.
Users are advised to never open emails from unknown contacts and to be wary of any messages from seemingly official organizations and institutions. Also, remember to keep Macros turned off at all times.