A particular type of brute force attack on a computer system. It involves the use of a program known as a war dialler. This generates a large number of sequences of characters that could be telephone numbers or passwords. A typical scanning attack would involve the program being set up to dial a long series of telephone numbers; any numbers giving some indication of a modem being used are stored. After a scanning session an intruder dials these numbers and attempts to break in using a variety of techniques including trying well-known passwords.