Is creating a botnet server in itself considered illegal?

Question

This is all hypothetical, I'm not interested in making one, just the legality to it,

Answer 1

As in Wikipedia, "A botnet is a number of Internet-connected devices, each of which is running one or more bots". There is nothing illegal with having a network of bots, but what you use it for can be illegal under national law, as well as how you come to own the botnet.

https://www.atg.wa.gov/botnet-facts
https://en.wikipedia.org/wiki/Computer_Fraud_and_Abuse_Act
http://uscode.house.gov/view.xhtml?path=/prelim@title18/part1/chapter47&edition=prelim

needless to say, data theft, breach, etc are also illegal in most countries with proper cyber laws.