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Open Ports.

Posted on 2001-07-23
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Last Modified: 2010-04-11
I want to know how would I be able to close open ports on my computer.
I performed a port scan of my pc, and found serveral open and unidentified ports. And am interested in closing some of them.

Also, is there a site that I could go look at a listing for all ports and see what uses what port?
I know of the services file in Windows, but as you all know it only lists registered ports.

I once heard of a site that gave you a comprehensive list of most of the TCP and UDP ports.

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Question by:Protorian
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10 Comments
 
LVL 2

Expert Comment

by:scott_renton
ID: 6310269
The first step to closing a port, is to find out what opened it in the first place.  For instance, if you're running a web server, you're going to listen for requests on port 80, or 443 (for ssl communications).  SMTP servers will listen on port 25 for incoming connections, POP connections on 110.

http://www.iana.org/assignments/port-numbers

This is a list of well-known ports & their use.  Start here, compare your ports to this list, then find the programs that are running & listening on those ports, and stop them.
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LVL 41

Expert Comment

by:stevenlewis
ID: 6310716
also check out www.grc.com
shields up
and check out Zonealarm at www.zonealarm.com (free personal firewall, software)
for best results get a hardware firewall solution
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Author Comment

by:Protorian
ID: 6311074
I have installed a firewall.
And have ran the sheilds up test.

I want to know how to close the open ports.
The ports are still open.
Even though they are behind the zonealarm. I did a port scan from the same computer, and saw that the ports are still open.


Is this such a hard question?
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LVL 41

Expert Comment

by:stevenlewis
ID: 6311824
What ports are open? some need to be open like 80
scan your machine for viruses/trojans, as they may have opened these other ports for you
also unbind netbeui form you dialup adapter (or NIC if using dsl/cable)
disable file and printer sharing, and remove all un-needed protocols
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LVL 3

Expert Comment

by:Bruce_R
ID: 6312145
you already mentioned grc.com , there's a good tutorial on there at

http://grc.com/su-bondage.htm

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Author Comment

by:Protorian
ID: 6312802
Ok,
Let me put it like this.
The computer in question is a server. It does nothing but run a web server, ftp server and a web based email server.

Therefore I need to have ports 80, 21, 20, 8080, 43 and 8383 open.

The computer was hit by more than one trojan virii and we have gotten rid of the virii but some of the ports are still open.

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LVL 41

Expert Comment

by:stevenlewis
ID: 6314892
For a web server I strongly suggest a hardware firewall solution.
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LVL 5

Accepted Solution

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Droby10 earned 75 total points
ID: 6324248
once again, i'll recommend foundstone's fport utility.

http://www.foundstone.com/rdlabs/tools.php?category=Forensic

it will tell you what executable or library is bound to what port...then you can make an assessment as to whether it's detrimental or not, or malicious or not.  
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Author Comment

by:Protorian
ID: 6360283
Thank you a million..
I was able to analyze my problem and solve it.
Thankx
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LVL 5

Expert Comment

by:Droby10
ID: 6360428
anytime.  glad you were able to resolve the issue.
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