Just report to coinbase, they will block those IP address.You need to use 2 FA for your account.I am also a coinbase user.Using coinbase about 1 years ago, I am using mobile number verification system and mail verification system for log in into my account.so my account is 100% safe from hacker.you can use those method fro preventing future hacking issue.
It was an issue from my very beginning faucet times. Coinbase security worked great and corrected my mistakes. But I closed my account because I was not able to report those ips. The email that was given in notificatuon mail produced an automated answer, that support through this way is deactivated and I followed the link to the new support system. There I wanted to open a support ticket but was everytime leaded to faq. So I decided to close my account forever. Now I am good with a wallet where I keep my own private keys.