Malware goes undetected by hiding malicious code in uncommon MS Access format
0/64 detections on VirusTotal as of 05.08.2024
The VMRay Labs team has uncovered a malware that goes completely undetected for weeks by hiding malicious p-code in MS Access’ uncommon ACCDE format.
Microsoft Access allows users to export their databases to a “protected” format (ACCDE), promising to keep macros hidden and unmodifiable. This sample abuses that feature to hide its malicious backdoor: a compiled VBA macro designed to drop and execute a malicious PE file stored in the database.
No detections on VirusTotal
0 of 63
In a nutshell:
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The ACCDE format is rarely abused by attackers:not a single ACCDE file uploaded to VirusTotal in the last 90 days has a malicious verdict.
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VBA macros were compiled to p-code and execodes, complicating static analysis, but dynamic analysis still reveals malicious behavior
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Dropped PE file (“MW-Black-Shell”, only 5/75 on VirusTotal) connects to C2 and keeps waiting for commands to execute
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The PE file is not stored in the macros but in a table in the database
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Schedules itself to be executed at specific times (e.g., daily at 9:30)