Explanation/Notes: As depicted in the movie War Games , hackers use a technique known as war-dialing to locate telephone lines that have modems connected to them. The process begins with the attacker identifying the telephone prefixes used in the area where the target company is located. A scanning program is then used to try every telephone number in those prefixes, to locate those that answer with a modem. To speed up the process, these programs are configured to wait for one or two rings for a modem response before going on to try the next number. When a company sets the auto answer on modem lines to at least four rings, scanning programs will fail to recognize the line as a modem line.