I've just been bugged by the mod_security plugin for Apache. I wanted to paste a kernelmessage where '/proc' is mentioned. Sadly this request got silently dropped. couldn't see any issue, nor 403 and the likes. A quick look at the error log indicated this:
[Tue Feb 14 10:31:58 2012] [error] [client XXX] mod_security: Access denied with code 403. Pattern match "/proc/" at POST_PAYLOAD [severity "EMERGENCY"] [hostname "pfuender.net"] [uri "/"]
So I decided to quickly disable the mod_security for the IP that I'm using. You can do so by putting the following line within your .htaccess file.
SetEnvIfNoCase Remote_Addr ^8\.8\.8\.8$ MODSEC_ENABLE=Off
Thanks to this post: askapache.com/htaccess..
Cheers,
Raphi