Port Removal

[killugh]

Hello:

I am an intermediate IT support person for a high school computer lab. I'm having some trouble preventing students from accessing webmail. I thought the easiest thing to do would (rather than trying to ban 20,000 websites supplying email) would be to remove the ports that support webmail.

I've done some research into POP, etc. and discovered that ports 109, 110, etc. support web based mail activity. Could someone explain to me how these ports might be closed?

PS. I went into Network Connections, double clicked TCP/IP protocol, advanced properties. I found some filtering options in there and messed around but to no avail...

[Ge0ph]

I think web mail runs through port 80, the same as any other web site. If you block webmail by port you will also block web browsing. I very well could be wrong about this because I'm not sure how webmail works. But I believe it just sends a request to the server via the browser(port 80), the server assembles the page with the information and sends it back, no other ports are needed.

At any rate, port blocking should be done at the gateway for a fair sized network.

[killugh]

You're right about port 80. I used a proc called Cdcombobulator which blocked port 80. I couldn't use the HTTP protocol. I was wondering though if I could just block outgoing stuff, I.e. Outlook Express (POP3) stuff...without preventing regular Internet activity...

[Ge0ph]

Outlook express is not webmail.

However, if you block port 25 (SMTP) and 110 (POP3) you should be good to go.

How you do that on an individual machine I don't know, I do all of my blocking at my Linux firewall.

[gamehead200]

Why not just disable downloading? My school allows retrieving e-mail...

[killugh]

If I purchase a firewall and set it up between the lab's main switch and the direct Internet connection, I should be able to prevent the emails?

[Ge0ph]

If I purchase a firewall and set it up between the lab's main switch and the direct Internet connection, I should be able to prevent the emails?

And get a better understanding of how it work and much more.

You can acomplish what you want

You get to learn something new

Sounds like a win, win situation to me.

PS. for the best bang for the buck I would suggest finding an old computer and installing something like Clarkconnect, M0n0wall, IPCop or smothwall.

[MCT]

also, if you've never used a firewall, i would "play" with it first, cuz if u set it up & its done wrong, u wont be able 2 let any computer connect 2 u or u wont be able 2 connect 2 the net

regards