[opensuse] How to Block Public Proxies

Hi ! We have Squid installed as transparent proxy, and it blocks certain web sites. However, I we have seen some users use public proxies like ninjaproxy in order to visit these sites. Is there any way to block public proxies along with those annoying sites? Thanks in advance for any suggestion(s) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org