Any reason to do not block useragent libwww-perl? So far, it looks like 90% of harvester are using libwww-perl in the useragent. I kick them off, but am I doing the right thing?
The best thing is to send them a 403 response with a short explanation of why they were forbidden in the body of the message. This way, if a person is using Perl to write a legitimate bot for crawling websites, he will be told that he can crawl yours by changing the user-agent that Perl sends. I have spam protection on my website that ignores all spam regardless of the user-agent but if you are trying to prevent people harvesting your website for splogging then a 403 response is a better option.