So shell I worry about it or do I need to do some countermeasures?
Just ignore it, if your passwords are long enough and are NOT based on words that can be found in dictionaries. Change the passwords from time to time AND keep your sshd up to date.
If I have too many root login requests (>200) and I'am able to find out the attackers provider (with nslookup <ip-address>), I sometimes write an abuse report to the provider.
Most of these are attacks are script kiddies who are only successfull in case that your password is emty or matches the username
greets Boris
