A trojan dialer is a type of dialer utilized to commit fraud. It is malicious software in disguise. A Dialer also can cause Internet dumping, which means dropping the normal Internet connection and dialing another number, such as the 1900 premium rate or an International Direct Dialing (IDD) numbers. This causes users to be charged expensively per minute.
Techopedia explains Trojan Dialer
A dialer is a computer program that establishes a connection to the Internet or a computer network through an analog telephone connection or Integrated Services Digital Network (ISDN) network. A dialer isoften utilized by Internet Service Providers (ISP) to setup Internet connection to its non-broadband subscribers.
Trojan dialers often get installed to a user’s machine without the user’s consent or knowledge. A user usually gets to carelessly download the dialer when visiting hazardous websites such as pornographic, gaming, file sharing, software cracks, and illegal download of music and/or softwares. These hazardous websites often ask the user to install the software to get access to the website.