I have noticed large amount of traffic coming to my site from different IP's with user agent.
Mozilla/5.0 (compatible; SiteExplorer/1.0b; +http://siteexplorer.info/)
I don't have much experience with Apache servers and hope someone can explain to me how to actually block this from accessing my site with .htaccess file.
I tried with
SetEnvIfNoCase User-Agent "^siteexplorer?$" bad_user
Deny from env=bad_user
but it's not working.