Windows Messenger service

Messenger service is a network-based system notification Windows service by Microsoft that was included in some earlier versions of Microsoft Windows.

This legacy technology, although it has a similar name, is not related in any way to the later, Internet-based Microsoft Messenger service for instant messaging or to Windows Messenger and Windows Live Messenger (formerly named MSN Messenger) client software.

WinPopup sends messages from one Windows computer to another on the same LAN. It is available in all Windows versions from Windows for Workgroups 3.1 to Windows Me, but has never been included with Windows NT-based operating systems. WinPopup works by means of the NetBEUI protocol.

There is also a port to Linux with an extended feature called LinPopUp, which allows adding Linux computers to the set. Linpopup is an X Window graphical port of Winpopup, and a package for Debian linux. It runs over Samba. Linpopup does not have to run all the time, can run minimized, and its messages are encrypted with a strong cypher. The traditional Unix functional equivalent of WinPopUp would be the wall and write commands.

The Messenger Service was originally designed for use by system administrators to notify Windows users about their networks. It has been used maliciously to present pop-up advertisements to users over the Internet (by using mass-messaging systems which sent a desired message to a specified range of IP addresses). Even though Windows XP includes a firewall, it is not enabled by default. Because of this, many users received such messages. As a result of this abuse, the Messenger Service has been disabled by default in Windows XP Service Pack 2.

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