If a modem is used to connect to the Internet, careful control of the numbers it dials is necessary, as some malicious programs initiate calls to high rate phone numbers and as a result force users to pay large telephone bills.
Anti-Dialer prompts the user to confirm any number being dialed if the dialing has not been initiated by the user (i.e. it is started automatically) or if the number is not displayed explicitly and so it can be secretly substituted. In this way the component eliminates the risk of any unauthorized dialing of a ‘phone number.
A modem connection to an Internet Service Provider (ISP) server is often established automatically. To avoid having to confirm each connection manually, the ISP number should be added to the trusted list of phone numbers, as automatic calls to trusted numbers will not be blocked.