War driving, also called access point mapping, is the act of locating and possibly exploiting connections to wireless local area networks while driving around a city or elsewhere. To do war driving, you need a vehicle, a computer (which can be a laptop), a wireless Ethernet card set to work in promiscuous mode, and some kind of an antenna which can be mounted on top of or positioned inside the car. Because a wireless LAN may have a range that extends beyond an office building, an outside user may be able to intrude into the network, obtain a free Internet connection, and possibly gain access to company records and other resources.
Some people have made a sport out of war driving, in part to demonstrate the ease with which wireless LANs can be compromised. With an omnidirectional antenna and a geophysical positioning system (GPS), the war driver can systematically map the locations of 802.11b wireless access points. Companies that have a wireless LAN are urged to add security safeguards that will ensure only intended users have access. Safeguards include the use of the Wired Equivalent Privacy (WEP) encryption standard, IPsec, or Wi-Fi Protected Access (WPA), together with a firewall or DMZ.
The term derives from a somewhat similar approach to breaching the telephone system called war dialing. Breaching a private network may be illegal and at least one person has been prosecuted for it.