What is a dialer ? - Security Term

A dialer is a program that uses a computer’s modem to establish a dialup connection to the Internet. A connection is made by dialing a predetermined phone number. Malicious dialers are designed to use international or premium rate local phone numbers to make a connection bypassing the local Internet service provider. Their activity usually results in receiving high phone bills, as per-minute charges of most phone numbers used exceed 5 or 10 dollars.