Windows Messenger service

Linpopup is an X Window graphical port of Winpopup, and a package for Debian linux.

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.

[2] It was 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).

If access to the ports from outside a network is not blocked, it can lead to the aforementioned spam issue.

WinPopup, shown in the background, first appeared in Windows for Workgroups , together with several other network applications.
Example of Messenger service spam from 2007.