A booster bag is a hand-made bag used to shoplift, typically from retail stores, libraries, and any other location employing security detectors to deter theft. The booster bag can be an ordinary shopping bag, backpack, pocketed garment, or other inconspicuous container whose inside is lined with a special material.
An item is placed inside the booster bag (effectively a Faraday cage). Electronic security tags inside the bag then will not be detected from outside, as by security panels in the detector antennas at the store exit.
Booster bags have been used by professional shoplifters for several years. Using them, a shoplifter can steal dozens of items with very little effort. Although the bags inhibit security detectors, they do not inhibit traditional security cameras, guards, etc. and therefore a shoplifter using one can still be caught by law enforcement personnel.
In most states of the United States booster bags are considered a burglary tool and possession of them can lead to felony charges.