This hypothesis targets the execution of specific binary artifacts identified by the BJFntv13 YARA signature, which may indicate the presence of low-severity malware, cryptominers, or initial access tools that evade standard behavioral detections. Proactively hunting for these signatures in Azure Sentinel allows the SOC team to identify dormant or stealthy threats early, reducing the risk of lateral movement or data exfiltration before they escalate in severity.
rule BJFntv13
{
meta:
author="malware-lu"
strings:
$a0 = { EB ?? 3A [2] 1E EB ?? CD 20 9C EB ?? CD 20 EB ?? CD 20 60 EB }
condition:
$a0 at pe.entry_point
}This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
bdagent.exe or bdupdate.exe) during a scheduled patch window. The YARA rule may match specific byte patterns in the binary’s embedded configuration or signature database that resemble the target malware family.
bdagent.exe or bdupdate.exe, or exclude files located in the C:\Program Files\Bitdefender\ directory tree.vmware.exe or VBoxManage.exe) while performing snapshot operations or live migrations. The rule may trigger on temporary memory mappings or helper binaries used for disk image manipulation.
vmware.exe, VBoxManage.exe, or vboxservice.exe, and exclude files under C:\Program Files\Oracle\VirtualBox\ or C:\Program Files (x86)\VMware\.7z.exe or 7zFM.exe) during automated backup jobs or log rotation tasks that compress large binary files. The YARA rule may match the compression algorithm’s specific header bytes or the executable’s internal structure.
7z.exe, 7zFM.exe, or 7zG.exe, and exclude files in common installation paths like C:\Program Files\7-Zip\ or C:\Program Files (x86)\7-Zip\.MsMpEng.exe) while scanning a large folder of legacy application binaries. The rule may produce false positives