How can someone use my IP address?

My forums are vBulletin 3.5.4 with yesterday's latest security patch. I am monitoring my board in online.php and notice there is a Guest with my IP address. This Guest is trying to create an event (which causes an error message) or viewing the calendar at this very moment and I would like to know how someone could be using my IP and is there a security risk for me?

Thank you.

Jim

I am monitoring my board in online.php and notice there is a Guest with my IP address
Are you logged in?

Yes, I am always logged in. I didn't pay much attention until the "Guest" moved next to my listing and I saw the IPs were the same.

I added my IP to the deny list of my .htaccess file, which got rid of the guest and, as far as I know, it didn't return. But that sure bothers me. I wonder if it's just a matter of someone who knows me (and my IP address) who is messin' with me to prove he can cause trouble on my site. I have heard of IP spoofing, but thought it was an old trick that wasn't done much any more. I don't know much about it and worry. Maybe too much so.

well, I'd worry about it being a security issue if it happens again - do you know the individual and can verify or deny it was him or her?

No, I don't know who it is. It could be one of several people.