.htaccess user agents and website security

I have been looking around and trying to work out the best way to protect a few websites of mine.

Appart from the obvious manual monitoring of the site logs and banning extreme/suspicious activity. I have seen many posts etc. about banning user agents. Is this a good route to go down? and would it be a better idea too, instead off banning known bad user agents, just allowing the common mainstream ones such as IE, FireFox, Safari and Chrome?

http://www.javascriptkit.com/howto/htaccess13.shtml

Not worth it.

The User Agent is sent by the client, and is trivial to forge. There’s a Firefox add-on that adds alternate UA options to the menu, for example. If the attacker is writing a script, he can specify whatever UA he wants.

Check more discussion of this question.

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