well they have to have an ip addres..
Having an IP Address does not necessarily do much.
Back in the 80s, there was a movie called 'Sneakers'. With Robert Redford, Sidney Poitier, River Phoenix, Dan Aykroyd.
The same method that people use to make calls difficult to trace, good hackers use to cover their tracks by bouncing off several compromised servers to prevent people from pinning them down. And yes, I am using a fantasized story with regards to something that should be RL, but the fact is, some things portrayed in movies are things people will try and do to cover their tracks.
Meanwhile, even if you DO get the originator's IP, That person's IP might be behind an ISP shared pool, which is not necessarily assigned to one person. Current Cable and DSL ISPs DHCP their IPs to the users, and sometimes those change on a month to month basis, even under an always on situation. Unless you pay for a static connection, your connection is never going to have a static IP. Part of this is also to prevent certain people from abusing their lower consumer grade bandwidth with you hosting your own server when you should be paying a higher tier connection to do that.
In either case, the last hurdle will be geographic location. Attacks on one system in one country does not mean that country can pursue, legally, someone in another country. While it is a crime, the most one country can do is inform another country of being violated or attacked by someone within the offending country and even then, the offending country has to actually gather corroborating proof that the claim is true, otherwise it devolves into issues of who is telling the truth.
Remember, our current world affairs, even 'friendly' countries don't quite trust the other friendly country with certain things. In this era, information and cyberwarfare is the new Cold War. Each country would love to have their cyber hackers tagged and collected because those will be the people who will be part of the front lines trying to get the much needed information that combat needs at time.