How can I restrict access to my website via web services only?

Question

I am getting lots of spam in my website. Here are some modules I tried as a remedy:

1. Honeypot
2. Http BL

No luck yet however.

Now I decided to make the site available only for web services only, whereas the web services are done with Services module.

So how can I allow access to my website via services only? Is there something I can achieve this from .htaccess ?