How to ban crawlers, bot, fake user and allow only specific browser?

I'm trying to make a good web traffic filter, my goal is to ban all bots, crawlers, spiders, non-real users and allow only a specific browser.

I have done some tests in PHP, others in JavaScript, but I do not feel that it is totally well done. I would like the opinion of some expert. I think using a combination of PHP + JavaScript + robots.txt + .htaccess could do it.

I know that the user agent can be faked, but I would like to know if there is a better way to detect it. For example I would like to allow only users to use Mozilla Firefox (regardless of version).

All others browser should go to an exclusion list or sort of, this is like a filter.

What is the best way to do this? In short, detect the browser to allow only Firefox and avoid all fake users, robots, spiders, crawlers and other crap.

Ok then, let me try to provide some ideas here.

You should use a combination of techniques:

1. Robots will keep the legic crawlers out;
2. Use some Javascript validation on the client side to keep most crawlers out (these will rarely have the ability to run Javascript);
3. On you server side, use a user agent service to identify and filter the user agents as well;
4. Track IP addresses so that you can do one-off bans on "known offenders";

To expand a little more on #2, your landing page could use JavaScript to drop a cookie with a "known" value that can be mapped back to the originator. One example is to take the user agent and ip address and compute a hash. This can still be faked but most offenders would just decide to ignore your site rather than put the effort into bypassing your protection measures.

Hope this helps.