external port scanner to test firewall

[glenn]

To all,

Does anyone know of an external port scanner that works with linux? I
am looking for a way to test the security of firewalls in my router and
host boxes.

For the windows world, there were online services such as
http://scan.sygatetech.com and others. Is there a linux analog to this?

Glenn

[Jean-David Beyer]

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You might wish to try:

https://grc.com/x/ne.dll?bh0bkyd2

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[Glenn Smith]

Jean-David,

Thanks for this link to the GRC probe site. I got the same results for both my linux box and Windows laptop, which I assume means the measurements are taken at the router. All ports except 68 were in stealth mode, and the only other problem was the ICMP echo received a ping..

I also tested the system at www.pcflank.com. It found ports 135, 136, 137, 138 to be closed but detectable. These are related to the NetBIOS for my LAN, so I'll work on securing these.

Many thanks.

Glenn