I guess I should explain what I call a 'bot'. This is a robotic-like program that searches around for a place to live. I nicknamed it 'Herman the Hermit', like the hermit crab that doesn't have a home of it's own, but finds empty shells in the ocean to take over as it's own home.
Herman's job was to find a home for itself, and become a root-equivalent, or administrative, 'big-boss' user on that system. It would hide itself in the operating system, then wait until root-level (or administrative level) user logged in, and silently make itself a hidden little home in the system. It was smart enough to randomly name its process, and the 'port' that it listened to.
Ports, for the uninitiated, are connections to a particular computer. There are an almost unlimited number of ports in a system. For instance, a web server connects to a user that's 'browsing' via port 80. File Transfer Protocol (FTP) usually connects via port 21. Although there are standard port numbers that can be used, there are also unused port numbers, like 1844, that a program can 'listen' to; it's the decision of the program as to what port it listens to.
Herman was built to randomly grab an empty or unused port on the system it was infecting. It would also send out a very short coded message to one of my bogus email accounts, advertising where it lived (the IP address), and the port number it was listening to.
Now, you might think that a simple listing of used ports on a system would alert a system administrator to the presence of Herman on a system. But Herman was a bit more clever than that. Herman would not respond to just any 'knock' on the port door. The request had to be formatted in a certain way. For instance, suppose that Herman was set to listen to port 1456. Any normal request to that port, sort of an "are you there?" question, would return an answer by the program living on that port to respond 'yes I am'. But Herman would only answer if the question was something like "Abdgeg14 hello". Any other request would be met by silence. Without the secret password, Herman wouldn't respond to any request.