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by allentech

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hi,

how do you open and close ports? do you need a software? or web-based config of the the hardware involved can be used?

I have a medium sized network ( peer-to-peer ) and i hear and read about this security things about ports being under attack.

most of the operating system are win 98 SE/ME, i have to Red Hat Linux 7.3. I have a router (linksys dsl router ) w/c claims it is also a firewall, it can be configured web-based. I have 3 24-port switches.

all pc uses norton anti-virus 2003.

im i under attack, how can i protect my network? or am i just paranoid.

5 replies

by thechas

A little paranoia is good for the soul.

If you have the same Linksys DSL router that I have, the firewall is less than you expect.
The router firewall feature only works if you install Zone Alarm Pro on all PCs that will access the router.
Then, you can enable a feature in the router that restricts access to only those PCs using Zone Alarm. A workable, but less than perfect solution.

Firewall software, among other things, blocks your open ports.

Here is a link to 1 port list.
I am sure that there are several other port lists out there.
http://www.glocksoft.com/trojan_port.htm

Chas

by joseph moore

I agree with TheChas that paranoid is necessary in this job! If you have an open network, someone WILL find it and they WILL exploit it.
Now, all machines (PCs, switches, routers, etc) that talk IP have at least 1 open port (unless the machine is locked down completely). You need open ports for applications to communicate to the machine.
If a machine does not listen on any ports, then you can't interface with the machine and do anything.
For example, your Win98 machines will have TCP port 139 open (this is the file sharing port). Now, there are exploits that can be done against this port to a)gain illegal access to the machine, b)crash the machine c)format the machine d)just about anything else you can think of.

Your switches (if they are configured) could have TCP port 23 open for Telnet. If your router/firewall is not configured properly, it could be possible for a remote attacker to hack into the switches and re-configure them. Or bring them down.

The first thing you needto do is secure your perimeter defenses at the router. Set up the firewall on the router. Since TheChas stated that the firewall capabilities on that router are not very good, then you need a real firewall NOW. Get one, lock it down to prevent unauthorized access.

Then you can worry about internal-based attacks, because according to studies, the INTERNAL hacker is more dangerous than the external one.

Good luck.

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