How to block the yahoo messenger in linux firewall

Hi,

My name is Ramprabhu working in a small company in bangalore.
Now got the task of blocking the yahoo messenger in my company's windows machine.

Since our company is smallone we r using the linux open source firewall.

so plz anyone tell me how to block the yahoo messenger in the linux firewall

I tried by blocking the ports which is used by the messenger.

PORTs ARE 5000:5050 (protocol) tcp.

But it also using the port 80 also , so it is the problem for me.Because our firewall acting as SQUID(proxy server). So i cont
block the port 80 in the iptables.

Plz give me idea for how to block the messenger application


How to block the domain names in my firewall Can u tell me plz

Welcome to firewall.cx, iamprabhu100. Blocking instant messengers at the gateway is always a bit tricky.

Most of these programs are quite persistent in finding ways out of your network. If their standard ports are blocked, they usually try to go out on port 80, which you may not be at liberty to block.

You could try blocking the following domain names if your firewall supports filtering by hostname:

scs.msg.yahoo.com
scsa.msg.yahoo.com
scsb.msg.yahoo.com
scsc.msg.yahoo.com
http.pager.yahoo.com

Ultimately, the best way of restricting access is by locking down your users' machines. I run all my users in non-admin mode so they can't install unauthorised software.

Welcome to firewall.cx, iamprabhu100. Blocking instant messengers at the gateway is always a bit tricky.

Most of these programs are quite persistent in finding ways out of your network. If their standard ports are blocked, they usually try to go out on port 80, which you may not be at liberty to block.

You could try blocking the following domain names if your firewall supports filtering by hostname:

scs.msg.yahoo.com
scsa.msg.yahoo.com
scsb.msg.yahoo.com
scsc.msg.yahoo.com
http.pager.yahoo.com

Ultimately, the best way of restricting access is by locking down your users' machines. I run all my users in non-admin mode so they can't install unauthorised software.

How to block the domain names in my firewall Can u tell me plz

You can block by hostname in iptables by simply using domain names instead of IP addresses. Alternatively, you could also achieve the same effect by creating some acls in your squid.conf file.

An example acl in your squid.conf to block the yahoo subdomains listed above would be:
[code:1]acl blockyahoo dstdomain scs.msg.yahoo.com scsa.msg.yahoo.com scsb.msg.yahoo.com scsc.msg.yahoo.com http.pager.yahoo.com[/code:1]

*.yahoo.*

-^

Hi ,,

Is there any person to give me idea related to this topic
further in detail.



regards,
Prabhakaran.D