Chat ports to block

[ra_sriniketan]

I have a linux red hat net server with squid running as its proxy.I want to block the ports of chat clients like yahoo messenger,rediff bol,gtalk etc.Please suggest in details.

 

[slugger]

if u block them u shud b able to block access thru d clients but if u dont block port 80[HTTP], ur users r gonna have a free run

ports used by d clients

Yahoo Instant Messenger 5050

MSN Messenger 1863

AOL Instant Messenger (AIM) 5190

Skype Ports above 1024 or Port 80 and 443
[dis last info has been shamelessly ripped from d url posted by mehulved. just trying 2 provide concise references 4 all clients and ports dey use. U DID ALL D HARDWORK]

 

[mehulved]

See *en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
Also, check /etc/services file
But, I believe they can still access it through web messengers or by tunnelling via http.

 

[ilugd]

if your client systems are in an administered environment, just give them limited accounts and block program access through firewall and remove permission to install programs.

 

[mehulved]

for skype *support.skype.com/index.php?_a=knowledgebase&_j=questiondetails&_i=148

 

[slugger]

if your client systems are in an administered environment, just give them limited accounts and block program access through firewall and remove permission to install programs.

but d00d
if port 80 is kept open, it is a child's play 2 use a web-based client 2 chat
and all outbount chat data wud b routed thru dat port

and blocking port 80 is pretty much senseless, wudnt u agree??

i actually thot of a reverse engineering trick 2 block port being accesed bychat client

BUT SORRY M8 IT IS A WIN-BASED SOLUTION

u must actually make use of a port forwarding tool to make it work

u cud use PFConfig to identify d port dat needs 2 b forwarded 2 make a program work and once d prot is idd u cud easily block it

BUT DIS BLOCKING THINGY WUD ONLY BLOCK CLIENTS INSTALLED ON UR COMPUTER

i actually found dis site 4 doing port forwarding in linux

u cud chk it out here

i dint bother 2 read it, 'cause i have absolute no use of linux right now

u cud go thru it and c if it help u id ports

 

[ilugd]

blocking individual web based messenger sites would be rather easy don't you think if you went through the logs atleast once a week. Squid does allow access to individual sites, doesn't it?

 

[slugger]

sum 1 is always discoverin [or codin] a new client every other day with features 2 boggle d human mind

 

[mehulved]

ilugd, yes that's possible. But then people could tunnel the traffic over http. Or many other ways. There isn't a fool proof way, I believe.

 

[ilugd]

oh, no fool proof way, I agree. The universe has the capability to create exceptional fools.

 

[ra_sriniketan]

k.I got the port numbers.Now tell me how to block the ports in squid via ACL.

 

[slugger]

chk if dis helps

 

[ra_sriniketan]

Got the configuration changes dirctives.It says:
acl block_port port 1234
http_access deny block_port
http_access allow all

But can someone plz tell where to write this configuration directives in ACL?Because ACL has big list of configuration directives.Plz help.