Re: blocking ports -- MIDRANGE-L

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I had a same problem with ICQ. But if it works like ICQ then it can uses many different ports when it has problem with default (5190) even 21, 23 which was really surprising for me. You can find outgoing connections simply via unix NETSTAT command (it works in Windows command line also). That's how i found open ports.

Erik Jahn

----- Original Message -----

From: Hall, Philip

To: 'MIDRANGE-L@midrange.com'

Sent: 21. b�ezna 2001 19:01

Subject: RE: blocking ports

> We would like to block the use of instant messengers by blocking

> the port through TCP/IP that they come in on. Does anyone know

> how to determine what port these messengers use?

If this is for external access, shouldn't this be the other way around, you should block every port at the firewall, then only open the ones you know are needed, basically just port 80 for HTTP, and maybe 21 for SMTP.

If you are trying to restrict traffic on your internal networks then you can determine the ports by running netstat -a on the PC before running AOL IM and again while it's running. comparing the two will show you the ports used.

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