Security Question

Hi, I run some wordpress blogs that I write on and lately they have been getting hacked on a regular basis. Redirection code is being put into some of the php files. I keep trying to change permissions and run scanners but I'm not sure that my measures are working. Plus, if I tighten the permissions down too tight, I can't post on the blogs at all.

I read on a site that hostgater has good security to fight things like this, so I'm considering switching. Just wondering if anyone has had any experience like this? Thanks.
Cynthia