Malicious programs of this type are designed to send messages to inform the malicious user controlling it when an infected computer is online. The malicious user will receive information about the infected computer, such as its IP address, the number of the open port, email addresses, etc. The information can be sent by a range of methods: email, a specially crafted request sent to the malicious user’s website, or via instant messaging.

Notifiers are used in multi-component Trojans in order to notify malicious users of the successful installation of malicious programs on victim computers.