squid/iptables -- plz help

[Maaz]

Hello Gurus,

on my lan i m running 10.x.x.x network.

os: rhl 9.0, squid n iptables r running.
local IP of the iptables/squid server: 10.0.0.254.

on the squid server machine(10.0.0.254)i did the following
1. echo 1 >/proc/sys/ipv4/ip_forward
2. iptables -t nat -A POSTROUTING -s 10.0.0.0/8 -o ppp0 -j MASQUERADE

now clients are connected to internet via 10.0.0.254.

1) now is it possible to block yahoo messenger, and webcam ? if so how ? i mean is it the squid's matter ? or iptables are responsible to block ymessenger and ymessenger's webcam ? and HOW ?

2) how can i block all images(gif, or jpeg) on every destination, i.e. I want to block all banners/adds and other images on every website for some of my users

plz help

Thanks in Advnce.
Regards
Maaz

[Maaz]

...and one more question
how can i block/deny downloading for some/all of my Internet-clients only at certain time e.g in between 6:00 pm and 11:30 pm

Regards
Maaz

[KristofH]

I recommend having a look at shorewall (for example), wich will do alot of things for you..

http://www.shorewall.net

Blocking images has to be done in squid, I guess you'll find the answer to that pretty fast if you have a look at the squid docs or do a google-search.

Cheers!

[Maaz]

Hi Kristof Hardy
Many Thanks for ur prompt reply.

I m reading squid docs but no success yet .. i.e. i didnt find any help from squid doc to block images
I'll try my best to work on shorewall.

[Maaz]

still eagerly looking forward for more help/reply

[Oliver Schwank · Accepted solution]

Hello,

you need some additional tools for squid. I use to block advertisments:

http://www.zaplet.org/adzapper/

To block more traffic in different ways, use:

http://dansguardian.org/

There are more of these programs out there, one is called squidguard. You can find them on freshmeat.net. They all integrate in squid.

I use adzapper (it is integrated in my Debian distribution) and find it totally sufficient.

Bye

Oli

[Muthukumar_5]

when squid is running with ip-tables, blocking yahoo messenger and webcam. We have to work with iptables to block yahoo messenger server ip-address. Same thing to y! messenger webcam.

we can block images as,
acl image urlpath_regex \.gif$ \.jpeg$
http_access deny image

To effectively make this, use dansguardian opensource tool to block banner/adds and images.

hth.

[Maaz]

Dear Oli I m highly thankful to u for the help, squidguard and dansguardian are both excellent.

Dear Muthukumar thanks a Million for the help. One more question ... is it necessarry to write a $ sign after gif and jpeg as in 'acl image urlpath_regex \.gif$ \.jpeg$'

I once reading the squid docs there i found like
acl blkurl url_regex ^http://www.i.com/foo.html$
i wana know... is it necessary to write a '^' Sign b4 the url and a $ sign at the end of the url ?

Thanks
Regards
Maaz

[Muthukumar_5]

acl type urlpath_regex is based on regular expression. To make a 100% correct match we have to use appropriate regular strings for that.

^ (cap) -- used to give the starting of the string pattern

$ (end) -- Used to indicate the end of string patter to be used.

. (dot) -- It is a wild-card character on shell so that \ used to deactivate it's wild-card functionality and give normal meaning to . (dot).

To filter .gif,.jpeg files then,

\.gif$ \.jpeg$ is needed.

You can get to know by using regular expression man page.

hth.

[Maaz]

Nice Help/explanation Dear Muthukumar.

Thanx
Regards
Maaz