Every coupe of weeks my the websites on my web server are infected with spam being inserted into the html pages. i am fairly certain this is being done through the blogs provided by wordpress. The blogs themselves are hosted on the web server, not wordpress. Could that be an issue?
Could another issue be the themes i am using? They are user created, and I find them when searching for themes. If they are not up to date or just old, is that enough of an opening for hackers/spam to start?
What other advice can you give me about this problem?