Web Proxy Server
stalking
tracking cookies
A network sniffer.
That actually depends upon what it is that you are using. If you use someone's car without permission, that is called stealing. If you use someone's movie without permission, that is called piracy. If you use someone's body without permission, that is called rape.
A person who enters by force without permission is commonly called a trespasser or an intruder.
When you take a picture of someone without their permission, it is called "unauthorized photography" or "invasion of privacy."
The term for taking pictures without permission is called "unauthorized photography" or "unlawful photography."
The first known spyware program, called "CoolWebSearch," was released in the early 2000s. This malicious software was designed to gather information about a user's browsing habits without their permission.
Counterfeiting
Use of protected material without permission or an exemption in the law is called infringement.
Certainly, it is called theft.
Copying someone else's work without permission is called plagiarism.