The wrap program is invoked with all of Bob's privileges—in particular with ownership of br , the cat-egory that restricts read access to Bob's files. wrap al-locates a new category, v, to isolate the scanner, creates a private /tmp directory writable at taint level 3 in cat-egory v, then launches the scanner tainted 3 in category v. The v taint prevents the scanner, or any process it cre-ates, from communicating to the update daemon or net-work, except through wrap (which has untainting privi-leges in v). The v taint also prevents the scanner, or any program it spawns, from modifying any of Bob's files, because those files are all less tainted (at the default level of 1) in category v.