[CentOS] How to block Yahoo , MSN messanger and Kazza with IPTABLES

Stephen John Smoogen smooge at gmail.com
Thu Nov 9 16:50:20 UTC 2006

On 11/9/06, Indunil Jayasooriya <indunil75 at gmail.com> wrote:
> Hi,
> I want to block  Yahoo Messenger, MSN messanger and Kazza with IPTABLES as
> my local network users always go there.
> How Can I do it?

Kazza and other Peer to Peer need something like a Layer 7 tool
because they are very closed. The Yahoo and MSN can be blocked by
blocking particular IP/ports.. HOWEVER, they all have web clients so
that they can just use a browser instead.

The true fix of this is the following:

1) A clear rule with consequences for using these tools on your
network. E.G. if at a company, they need to register a need to use the
tool, get clearance to use it and then are monitored to use it. People
who do not have a clearance to use it will be detected and disciplined
(fired, demoted, whatever HR says needs to be done).

2) Set up the firewall to block/detect usage of the tools. Make a
daily/weekly report to HR of people abusing the rule.

3) Follow through with step 1. If #1 has no teeth, then you might as
well just hang it up as the number of ways to get around firewalls
these days is enormous (e.g. if your firewall doesnt block all
outgoing traffic unless approved you are hosed :)).

Stephen J Smoogen. -- CSIRT/Linux System Administrator
How far that little candle throws his beams! So shines a good deed
in a naughty world. = Shakespeare. "The Merchant of Venice"

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