Secure USB Port Blockers Protect Your Data Against Unauthorized Access These port blockers are an easy way to prevent unapproved personnel from connecting an unwanted flash drive or other USB peripheral to a USB-A port. Use the included security key to insert a blocker into the USB port and lock it into place. This will prevent any USB peripheral from infecting the device with malware or removing classified data. The key also removes the blocker just as easily and quickly as it installs the blocker. Four blockers are included, three of which conveniently store inside a compartment on the key. The key and blockers can only be used together for maximum security.