Need help!!

So we have this cs 1.6 server running really good with decent ammount of players.I am rank Owner(second best after Powered) so I get access to server files via ftp lately my pc broke (psu burned) and at the same day people and Powereds see me online "abusing powers" I changed my password to my nick in ftp to a really long 28 character password still sb was.able to log on.That means he has access to server files... (there are like 6-9) people who have acces to that so theres nothing I can do about him.having acess but 1 question. How do I get the person thats logging with my nick's ip so when he joins with his real nick I'll perm ban it.Any way to do that???