A host protects slaved devices. Everything connected to the host is part of its wide area network (WAN), so it's protected by the host's ratings. Blinding a camera, opening a maglock, controlling the elevators, turning out the lights, activating the fire sprinklers ... all of these are Control Device actions requiring marks on the host and opposed by the Host Rating + Firewall.
BUT ... slaved devices also make a host vulnerable. If you make a direct connection to a slaved device with a universal data connector, then you bypass the host ratings and target the device itself, with only its Device Rating + Firewall (which probably also equals the Device Rating) to oppose you. And because the device is slaved to the host, gaining a mark on a device also gives you a mark on the host.
Patrol IC, like every other kind of IC, uses the attributes of the device or host on which it's running.