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 a Tripp Lite U2BLOCK-A-KEY security key (sold separately) 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. The U2BLOCK-A10-RD includes 10 red blockers, which can only be used with the key included with U2BLOCK-A-KEY.