You could make a new folder in /var/squidGuard/blacklists and add a couple of files that are similar to ones you already see there.
# For example: Chat ( messenger )
domains expressions urls
Your domain list file may start like this...
64.12.50.151
64.12.32.186
68.142.194.15
Your expressions list may look like this...
(chat|messenger|aim)
And url list file may look something like this...
http://www.aim.com/
messenger.yahoo.com
Don't forget to initialize the blacklists ( takes a loooong time )
squidGuard -C all
You might also consider adding an
acl regexp in squid.
Webmin is your friend!
.