This is something keep busy system administrator for few days questioning.
I have found no 100% list of bad bot online as it require to keep updated.
Here is my version, will try to update but can not guarantee.

Place below in the root of your server.

| .htaccess

SetEnvIfNoCase User-Agent "^Mozilla/4\.0\ \(compatible\)$" bad_bot 
Order Allow,deny
Allow from all
deny from env=bad_bot

<code htaccess | .htaccess> RewriteEngine On RewriteCond %{HTTP_USER_AGENT} ^BlackWidow [OR] RewriteCond %{HTTP_USER_AGENT} ^Mozilla/4\.0\ \(compatible\) [OR] RewriteCond %{HTTP_USER_AGENT} ^Bot\ mailto:craftbot@yahoo.com [OR] RewriteCond %{HTTP_USER_AGENT} ^ChinaClaw [OR] RewriteCond %{HTTP_USER_AGENT} ^Custo [OR] RewriteCond %{HTTP_USER_AGENT} ^DISCo [OR] RewriteCond %{HTTP_USER_AGENT} ^Download\ Demon [OR] RewriteCond %{HTTP_USER_AGENT} ^eCatch [OR] RewriteCond %{HTTP_USER_AGENT} ^EirGrabber [OR] RewriteCond %{HTTP_USER_AGENT} ^EmailSiphon [OR] RewriteCond %{HTTP_USER_AGENT} ^EmailWolf [OR] RewriteCond %{HTTP_USER_AGENT} ^Express\ WebPictures [OR] RewriteCond %{HTTP_USER_AGENT} ^ExtractorPro [OR] RewriteCond %{HTTP_USER_AGENT} ^EyeNetIE [OR] RewriteCond %{HTTP_USER_AGENT} ^FlashGet [OR] RewriteCond %{HTTP_USER_AGENT} ^GetRight [OR] RewriteCond %{HTTP_USER_AGENT} ^GetWeb! [OR] RewriteCond %{HTTP_USER_AGENT} ^Go!Zilla [OR] RewriteCond %{HTTP_USER_AGENT} ^Go-Ahead-Got-It [OR] RewriteCond %{HTTP_USER_AGENT} ^GrabNet [OR] RewriteCond %{HTTP_USER_AGENT} ^Grafula [OR] RewriteCond %{HTTP_USER_AGENT} ^HMView [OR] RewriteCond %{HTTP_USER_AGENT} HTTrack [NC,OR] RewriteCond %{HTTP_USER_AGENT} ^Image\ Stripper [OR] RewriteCond %{HTTP_USER_AGENT} ^Image\ Sucker [OR] RewriteCond %{HTTP_USER_AGENT} Indy\ Library [NC,OR] RewriteCond %{HTTP_USER_AGENT} ^InterGET [OR] RewriteCond %{HTTP_USER_AGENT} ^Internet\ Ninja [OR] RewriteCond %{HTTP_USER_AGENT} ^JetCar [OR] RewriteCond %{HTTP_USER_AGENT} ^JOC\ Web\ Spider [OR] RewriteCond %{HTTP_USER_AGENT} ^larbin [OR] RewriteCond %{HTTP_USER_AGENT} ^LeechFTP [OR] RewriteCond %{HTTP_USER_AGENT} ^Mass\ Downloader [OR] RewriteCond %{HTTP_USER_AGENT} ^MIDown\ tool [OR] RewriteCond %{HTTP_USER_AGENT} ^Mister\ PiX [OR] RewriteCond %{HTTP_USER_AGENT} ^Navroad [OR] RewriteCond %{HTTP_USER_AGENT} ^NearSite [OR] RewriteCond %{HTTP_USER_AGENT} ^NetAnts [OR] RewriteCond %{HTTP_USER_AGENT} ^NetSpider [OR] RewriteCond %{HTTP_USER_AGENT} ^Net\ Vampire [OR] RewriteCond %{HTTP_USER_AGENT} ^NetZIP [OR] RewriteCond %{HTTP_USER_AGENT} ^Octopus [OR] RewriteCond %{HTTP_USER_AGENT} ^Offline\ Explorer [OR] RewriteCond %{HTTP_USER_AGENT} ^Offline\ Navigator [OR] RewriteCond %{HTTP_USER_AGENT} ^PageGrabber [OR] RewriteCond %{HTTP_USER_AGENT} ^Papa\ Foto [OR] RewriteCond %{HTTP_USER_AGENT} ^pavuk [OR] RewriteCond %{HTTP_USER_AGENT} ^pcBrowser [OR] RewriteCond %{HTTP_USER_AGENT} ^RealDownload [OR] RewriteCond %{HTTP_USER_AGENT} ^ReGet [OR] RewriteCond %{HTTP_USER_AGENT} ^SiteSnagger [OR] RewriteCond %{HTTP_USER_AGENT} ^SmartDownload [OR] RewriteCond %{HTTP_USER_AGENT} ^SuperBot [OR] RewriteCond %{HTTP_USER_AGENT} ^SuperHTTP [OR] RewriteCond %{HTTP_USER_AGENT} ^Surfbot [OR] RewriteCond %{HTTP_USER_AGENT} ^tAkeOut [OR] RewriteCond %{HTTP_USER_AGENT} ^Teleport\ Pro [OR] RewriteCond %{HTTP_USER_AGENT} ^VoidEYE [OR] RewriteCond %{HTTP_USER_AGENT} ^Web\ Image\ Collector [OR] RewriteCond %{HTTP_USER_AGENT} ^Web\ Sucker [OR] RewriteCond %{HTTP_USER_AGENT} ^WebAuto [OR] RewriteCond %{HTTP_USER_AGENT} ^WebCopier [OR] RewriteCond %{HTTP_USER_AGENT} ^WebFetch [OR] RewriteCond %{HTTP_USER_AGENT} ^WebGo\ IS [OR] RewriteCond %{HTTP_USER_AGENT} ^WebLeacher [OR] RewriteCond %{HTTP_USER_AGENT} ^WebReaper [OR] RewriteCond %{HTTP_USER_AGENT} ^WebSauger [OR] RewriteCond %{HTTP_USER_AGENT} ^Website\ eXtractor [OR] RewriteCond %{HTTP_USER_AGENT} ^Website\ Quester [OR] RewriteCond %{HTTP_USER_AGENT} ^WebStripper [OR] RewriteCond %{HTTP_USER_AGENT} ^WebWhacker [OR] RewriteCond %{HTTP_USER_AGENT} ^WebZIP [OR] RewriteCond %{HTTP_USER_AGENT} ^Wget [OR] RewriteCond %{HTTP_USER_AGENT} ^Widow [OR] RewriteCond %{HTTP_USER_AGENT} ^WWWOFFLE [OR] RewriteCond %{HTTP_USER_AGENT} ^Xaldon\ WebSpider [OR] RewriteCond %{HTTP_USER_AGENT} ^Zeus RewriteRule ^.* - [F,L]