We are using squid web cache transparent proxy in our company and we usually have 450 users browsing during peak hours. We get lists of URLs (upto even 1600 URLs per list) from the national telecom authority for blocking. We block them using Squid ACL with a black list file but we experience significant performance degradation as soon as we apply the ACL in squid.conf. What is the remedy of this problem? How can we block such huge number of URLs?.
So. you are experiencing a performance issue with squids native acl.
What version of squid are you using and what about specs on the box?
I am also curious if you are getting warnings in your logs when you reconfigure or restart squid when you apply new blacklists.
Keep in mind that .somesite.com also blocks all subdomains from the TLD down, so there is no need to have crap.somesite.com and .somesite.com, it will cause performance issues and flood out your log files. If this is an issue for you, make sure you parse out all the dupes/subs and keep only tlds in there unless otherwise neccesary to only have a sub blocked.
Also, have you tried the squid-prime blacklist from squidblacklist.com?
Whenever the Squid configuration is reloaded, everything Squid does is paused.
I suggest to use ufdbGuard, a free URL filter for Squid. When ufdbGuard reloads the URL database there is no negative effect for Squid or users browsing. One can download ufdbGuard from SourceForge and URLfilterDB.