There are a number of laws regarding hacking a computer you don’t have authorization to hack, the CFAA in the USA, the CMA in Great Britain, the CHM in Australia, and the list goes on. All of which make it illegal to do what you want to do, and in some cases have pretty strict penalties for even the smallest of actions.
The term most often used to describe what you’re talking about is Hacking Back. It’s part of the Offensive Countermeasures movement that’s gaining traction lately. Some really smart people are putting their heart and soul into figuring out how we, as an industry, should be doing this. There are lots of things you can do, but unless you’re a nation-state, or have orders and a contract from a nation-state your options are severely limited.
There’s always an “Abuse” email address on the whois of a netblock for reporting misuse of an IP address.
You can use http://whois.domaintools.com/ to do a whois lookup to get the address.
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