Suspicious File System Access by Non-System Accounts

Ankit Mehta@Secvyn

•updated Jun 17, 2026•0•0•1

This rule detects suspicious access attempts to file system objects (hard disk volumes or DOS devices) by non-system accounts. It specifically looks for Event ID 4656 (Handle to an Object was Requested) where the ObjectName contains "\Device\HarddiskVolume" or "\DosDevices\", the AccessMask indicates broad access (0x1fffff or 0x120089), and the SubjectUserName is not a standard system account (SYSTEM, LOCAL SERVICE, NETWORK SERVICE). The rule then aggregates these events over one-hour intervals and flags if five or more such access attempts occur from the same computer and user.