I might talk through one's hat, but Nasomi most likely holds a list of the IPs each person has ever used to login, and when someone logs in using a new IP, it will be cross checked with all the IPs that was used by other users playing on Nasomi. If there's a match or multiple matches, all these accounts will be linked together. They are said to be linked because if one of the person in one group violates a rule and is jailed or banned, every other account in the group will receive the same punishment. (because they will be assumed to be the same person)
There might also be some intelligence behind it, like frequency IPs are used and stuff to categorize as a IP for a user.
I wouldn't spend too much time worrying too much about it, as there is 256^4 = 4 294 967 296 IPs in the world,
https://en.wikipedia.org/wiki/List_of_c ... allocationAnd disproportionally too many in the top 10 countries
If you were to get banned eventually because you played for a few hours on a IP that a cheater eventually got, and got banned, I'm sure Nasomi would unban you