because I set it to use static IP and thought it would never change.
The worst thing was that the former owner of my new IP used to run a pretty busy web site, so I got a lot of hits from all over the world (esp. from search engine).
Anyway, I got another IP now after switching to Shaw. So I got my IP changed twice.
Just FYI, if you are going to put your machine directly on the Internet, be sure to update it to the lastest patch. I heard that a stock installation of Redhat got hacked after only one or two weeks of exposure on the Internet.