10
It's a good idea to keep user agents that identify themselves as Perl (or pycurl) off your server. Perl has perfectly valid applications, but sadly from our log, 100% of these requests are trying to access forbidden files, or install back doors by targetting files with known vulnerabilities, like the older spaw control class.
The UA can be cloaked, but it's surprising how many leave 'libwww-perl' in the string. We reduced intrusive traffic by thousands of requests simply by adding an htaccess file to the root directory containing:
SetEnvIfNoCase user-agent "^.*(libwww-perl|curl|pycurl).*" getout
<Limit GET POST>
Order Allow,Deny
Allow from all
Deny from env=getout
Limit>
If your server supports MOD_REWRITE you can alternatively use that method to redirect the request, but the above should work on all Apache servers.
Of course the cloaked requests still get access, so we are currently testing
The Perishable Press 4G Blacklist on a few XOOPS sites. This addition to htaccess (or httpd.conf) focuses on blocking illegal character use in the request rather than blocking user agents, which of course can be completely forged.
From the feedback, it appears that the content may need to be adjusted to suit certain applications (some Joomla users have had to remove a few blocked chars) but it looks really worthwhile.
HTH
