Someone keeps sending me IMs but won't say who it is, and they get through my security settings

Every day I get an IM from someone that says the same thing, Hi Sexy. That's it, and they won't answer me back. I don't know if it's someone I know or don't know, but they seem to know a lot about computers because they get through every security setting I have. They get past Ignore all the time. They aren't on my buddy list that I know if. And I tried to track down who it is, but they give such a crazy user name that Yahoo says it can't find out who it is. So what do I do? I don't know if this person is just harassing me or really is interested or just a creep. Can someone give me some ideas? Is there any way I can find out who it is and where it is coming from? Is there any way to track the IP address back to the original server, because I'm tired of if. I want to know who it is. It could be someone on my buddy list, but my buddy list is short and the people on the list are usually sleeping when I get these IMs. They also change the username which is just a bunch of letters. Help.

Someone keeps sending me IMs but won't say who it is, and they get through my security settings. Help!?free spyware remover

i really dont know but if i was u id get expert help with this its creepy

Someone keeps sending me IMs but won't say who it is, and they get through my security settings. Help!?ktm