Port forwarding/open ports?

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To be able for another person to connect to my Netmeeting (conf.exe)in
Windows XP and share applications I would need to open the ports 1720
and 1503 in my router firewall.

My wonder is how much more vulnerable I will be if I do that? It would
be nice not to have to open and close those ports over and over again in
my router firewall when I need it and instead having them open all the
time so it will just be to start Netmeeting when I need to collaborate
and share applications.

- Is it just a risk (bigger or smaller?) when I have Netmeeting started
since I suppose some good hacker would need an application that actually
listens to those open ports to be able to do anything? If I normally
don't have Netmeeting started I suppose the ports could just as well be
open in my router all the time?

- If it is a risk as described above, what if I create a rule in my
software firewall that blocks those two ports on the computer in my LAN
to which the ports are forwarded? It is quicker for me to put that rule
on and off in my software firewall than to open and close the ports in
the router.

- These same questions above goes for the one port one can choose to
have open in the router to give the best possible chances for good sound
quality for Skype IP calls. How risky or not is it to have a few ports
open in you router firewall?

Re: Port forwarding/open ports?

Depends on what applications are listening.  If no application is
listening then the system will send back an error to the remote point.
So a vurnerability would have to be in the IP stack before the firewall

Re: Port forwarding/open ports?

AV wrote:
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good idea. that is just as safe or unsafe as what you mentioned above.
But it is more convenient. As long as you only have netmeeting running
when you need it.

you could improve it by setting your "home routers" firewall to only
allow your friend's ip to connect. nobody else.   but then if your
friends ip changes, it's a nuisance. I think many broadband IPs tend to
remain constant for ages, prob depends on the provider.

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I think what you wrote there doesn't make sense

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correct, good idea.

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part of what you wrote there doesn't make sense. But you're hintin
towards a good idea.
Set your firewall to block everybody from connecting , except for your
friend's IP.
then even if you did have netmeeting open all the time, and ports
forwarded by your router permanently, your firewall would (try to)
protect your computer. Pretty safe. Safest thing is that + not having
netmeeting running all the time.
I think it's unnecessarily to go to the lengths you showed some
distaste for, the idea of setting port forwarding each time you want to
use netmeeting. Better to just run netmeeting when you need it.

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same. if the software isn't running then it's certainly ok.

I guess that if your comp was exploited then malicious software could
use those ports though. so perhaps not so safe.  to have loads of ports
forwarded.  At he same time it may nto be so feasible time wise to keep
forwarding the right ones each time you use the software. it's a

Re: Port forwarding/open ports?

AV wrote:
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Some ports have to be open to operate.

It's as risky as the software exposes the system to.

I frequently use dynamically open ports by scripting the open an close
in batch file that call the program in question.

For example skype has the following vulnerabilities listed:

Search Advisory, Vulnerability, and Virus Database

Search: [Advanced Search]

All Content Secunia Advisories Virus Information

View full vulnerability report for a specific product:
- Skype for Linux 0.x
- Skype for Linux 1.x
- Skype for Mac OS X 0.x
- Skype for Mac OS X 1.x
- Skype for Pocket PC 1.x
- Skype for Windows 1.x

Found: 3 Secunia Security Advisories, displaying 1-3

Sort by: Match, Title, Date

Title    Date
Skype Multiple Buffer Overflow Vulnerabilities    2005-10-25
Skype "skype_profile.jpg" Insecure Temporary File Creation    2005-07-18
Skype "callto:" URI Handler Buffer Overflow Vulnerability    2004-11-15

Found: 5 Viruses, displaying 1-5

...Suspended. We've got something we would like to share with you. Skype
for Windows 1.4 - Have you got the new Skype? What is...
Report from McAfee. On 19th Oct 2005.
...ort@[RECIPIENT MAIL DOMAIN] Subject: One of the following: Share
Skype. What is Skype? Skype for Windows 1.4 - Have you got...
Report from Symantec. On 17th Oct 2005.
...ionally, Samony.A spreads via email in a message that deals with
Skype , which is a telephony over IP program. Visible Sympt...
Report from Panda Antivirus. On 26th Oct 2005.
...e firewall settings. Distribution Subject of email : Skylook for
Skype Name of attachment : skylook_1.exe Size of attachment...
Report from Symantec. On 25th Oct 2005.
...ed, it performs the following actions: Copies itself as
%System%\skype32.exe. Note: %System% is a variable that refers to th...
Report from Symantec. On 3rd Dec 2005.

(from secunia http://secunia.com/search/?search=skype )

All software opens the vulnerability window.  Many factors including the
software contol the danger to the local system.  It depends if the
benefits outweigh the risk of use.

Not sure I have helped much but understand everything you use to
communicate on the web increases your risk of compromise.  How a tool is
used (user behaviour) can significantly increase that risk.  Opening
unknown executables, and communicating with unknown people always
increases the risk.


Re: Port forwarding/open ports?

On Mon, 30 Jan 2006 19:51:46 +0000, AV wrote:

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In your router, you should find something called "port triggering."  When
a program on your computer (like Netmeeting or Skype) creates a
connection, the router can be "triggered" to open that port, and it will
then close when no longer in use.  The ports are then only open while
you're using these applications.

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