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Blocking a TCP/IP connection

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by blerg 1 view

Closed to new repliesThis discussion is closed. It stays readable, but it takes no new replies.

Ok, I'm gonna throw this question out, and all input is welcome, even if it points out that I'm missing the obvious. ;)

For whatever reason, I suspect an unwelcome connection to my machine while online. From the command prompt, I type "netstat" to see the list of active connections, and I find one I can't account for; for instance:

proto local address foreign address
TCP my_machine:123 123.45.67.89:456

Is there a way I can block just that one connection? Or to close just port 123 on the local machine? I'd like a way to do this from the command prompt, but any way to accomplish the task would interest me.

Jim Peterson
JKP@att.net

11 replies

by sales

what you need is to set up a firewall. That will allow you to filteer and allow only the IP's and ports you choose and block the remainder. That should get you started , the rest depends on your OS

by blerg

Thanks for the reply. I know I can do this with a firewall, but I wanted to know if there were other alternatives I was overlooking. If this forum can't provide an answer, I'll accept that, because I get better quality input here than anywhere else I have tried.

by parbo

Answer 1 is correct. Blocking of ports is not done by the OS itself. So there is no internal command to block ports. You need a firewall.

by blerg

Thanks for your input, also. It's just my nature to keep trying to find alternative ways to accomplish things, regardless of whether or not they're possible. ;)

by big ray

The first 2 answers are pretty good, but can be expensive for good protection. Go get ZoneAlarm from Zone Labs. www.zonelabs.com. This nifty little program is free and makes your computer virtually invisibe to the world. Not only that if a program on your PC tries to access the internet when you are online, a big popup box appears telling you what is trying to access the net on what port and asks if you want to allow it. You have complete control of what goes in and comes out of your PC. It will also display messages when someone tries to ping or connect to your computer. It can also be turned off at will, and has an emergency shutoff switch so that if someone manages to get through, you can click a button and all network traffic isbrought to a halt.

I have been running it for almost 6 months now and I was even able to catch some worms that were on my PC that McAfee was not able to find.

by blerg

I thank everyone for their input, but what I was looking for does not seem to be an option.

by edward clint

If you are running win98SE, you have ICS available to you. ICS being windows Internet Connection Sharing. It is rudimentary proxy/firewall type software. You can choose to open or close or simply not respond on any port you want.
ICS while basic, is extremely well designed. Simple, free, easy. And the security will work whether or not you are sharing an internet connection.. though I have not tried this myself.

ZoneAlarm looks good too.

-EC

by blerg

I thank everyone for their input, but what I was looking for does not seem to be an option.

by jamesdbell

I have a cable modem at my house and I use Zone Alarm Pro, I HIGHLY recommend this product. I have used Black ICE, but this software makes it seem as though someone is always attempting to get into your PC. AOL ADs make this system seem as though someone is trying to get into my PC. I have used LockDown 2000, AWESOME TOO, detects trojans and informs you the second that someone makes contact with your PC. Hope this helps

by blerg

I thank everyone for their input, but what I was looking for does not seem to be an option.

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