Cybersecurity researchers have detailed widespread phishing campaigns targeting small and medium-sized businesses (SMBs) in Poland during May 2024, leading to the deployment of several malware families, including Agent Tesla, Formbook, and Remcos RAT.
According to cybersecurity firm ESET, other regions targeted by these campaigns include Italy and Romania.
“Attackers used previously compromised email accounts and company servers not only to spread malicious emails but also to host malware and collect stolen data,” ESET researcher Jakub Kaloč said in a report published today.
These campaigns, spread across nine waves, are notable for the use of a malware loader called DBatLoader (aka ModiLoader and NatsoLoader) to deliver the final payloads. This marks a departure from previous attacks observed in the second half of 2023 that leveraged a cryptors-as-a-service (CaaS) dubbed AceCryptor to propagate Remcos RAT (aka Rescoms).
“During the second half of [2023], Rescoms became the most prevalent malware family packed by AceCryptor,” ESET noted in March 2024. “Over half of these attempts happened in Poland, followed by Serbia, Spain, Bulgaria, and Slovakia.”
The attacks began with phishing emails incorporating malware-laced RAR or ISO attachments that, upon opening, initiated a multi-step process to download and launch the trojan.
When an ISO file was attached, it would directly lead to the execution of DBatLoader. The RAR archive, on the other hand, contained an obfuscated Windows batch script with a Base64-encoded ModiLoader executable disguised as a PEM-encoded certificate revocation list.
DBatLoader, a Delphi-based downloader, is primarily designed to download and launch the next stage malware from either Microsoft OneDrive or compromised servers belonging to legitimate companies.
Regardless of the malware deployed, Agent Tesla, Formbook, and Remcos RAT possess capabilities to siphon sensitive information, allowing the threat actors to “prepare the ground for their next campaigns.”
This development comes as Kaspersky revealed that SMBs are increasingly targeted by cybercriminals due to their lack of robust cybersecurity measures and limited resources and expertise.
“Trojan attacks remain the most common cyberthreat, indicating that attackers continue to target SMBs and favor malware over unwanted software,” the Russian security vendor said last month.
“Trojans are particularly dangerous because they mimic legitimate software, making them harder to detect and prevent. Their versatility and ability to bypass traditional security measures make them a prevalent and effective tool for cyber attackers.”
