Topic: Auto-Blocking users who post <a href="">, i.e. html links

I've noticed a lot of the automatic bots signatures, sometimes also posts, include <a href=""> links .
It's rare for a real user to make the mistake of posting html.

Maybe it would be good idea to temporarily ban/block any user that tries to post such links automatically?
Maybe have an email sent to the "offending" user telling him a moderator or admin needs to unblock his account?

Or is that to extreme?

Should maybe just a warning appear that tells the user that he needs to put such links in code tags?

Re: Auto-Blocking users who post <a href="">, i.e. html links

example of a standard spammer signature

<a href="http://www.foreignexchangestudentprograms.net/">foreign exchange student programs</a>
[url=http://www.foreignexchangestudentprograms.net/]foreign exchange student programs[/url]

the a href is what I'd like to search for and block when a user posts or uses signature....