Apparatus and methods prevent malicious data in Universal Serial Bus (USB) configurations by providing a hardware firewall. A hardware device interconnected between a host and the USB monitors communication packets and blocks packets having unwanted or malicious intent. The device may act as a hub, enabling multiple devices to connect to a single host. The device may only allow mass storage packets from a device recognized as a mass storage device. The device may block enumeration of unwanted devices by not forwarding packets between the device and the host. The device may be operative to assign a bogus address to a malicious device so as not to transfer communications from the device further up the chain to the host. The device may provide shallow or deep packet inspection to determine when a trusted device is sending possible malicious data, or provide packet validation to block packets that are malformed.