Usb

USBGuard is a security framework for Linux that controls which USB devices are permitted to interact with the system. It sits above the kernel’s native USB authorisation subsystem — a per-device authorisation flag in the USB core that determines whether a device can be configured and begin sending data — and enforces a policy defined in a rule file against every device that connects or is present at startup. The threat model USBGuard addresses is both insider threat (unauthorised storage devices, data exfiltration) and hardware attack: BadUSB devices — malicious firmware embedded in devices that present themselves as HID keyboards, network adapters, or other trusted classes — can be blocked by a sufficiently specific USBGuard policy that restricts which USB interface classes are permitted. A USB device that claims to be a keyboard (03:01:01) but was not explicitly authorised cannot send keystrokes; a USB storage device plugged into a workstation with a policy that only allows a specific keyboard and mouse is blocked outright. USBGuard cannot protect against devices present at boot (before the daemon starts), so it is a defence-in-depth control for the running OS rather than a substitute for physical port security.