Large Data Transfer to Removable Media Share

Darshan Thummar@Mighty

•updated Jun 12, 2026•0•0•5

This rule detects large data transfers (over 65000 bytes) to a Server Message Block (SMB) share that contains the string "USBSTOR" in its content. This combination suggests data exfiltration to removable media, as "USBSTOR" is often associated with USB storage devices. The rule uses a threshold of 20 such transfers within 60 seconds from the same source IP to trigger an alert, indicating a sustained large data transfer activity.