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Re: A Problem with Nmap - All Ports are classified as open no matter what IP address I scan
From: Professor 0110 <professor0110 () gmail com>
Date: Wed, 3 Jun 2009 19:52:42 +1000

Thanks for the reply! :)
If that is true, is this behavior generally illegal?

What should I say to my ISP?

Any further help will be appreciated!


Professor 0110

So, what you're saying is that my ISP is acting as a Firewall.
On Wed, Jun 3, 2009 at 7:15 PM, Patrick Donnelly <batrick () batbytes com>wrote:

On Wed, Jun 3, 2009 at 2:33 AM, Professor 0110 <professor0110 () gmail com>
Hi everyone,
I've been having this problem ever since I started using Nmap, but I
decided to ask for professional help until now.

Anyway, my problem is, whenever I scan an IP address with Nmap it
all ports as open, and ports 135, 139 and 445 as filtered. The only
exception to this case is when i scan my LAN . I am on a satellite
connection. However, whenever I use an alternate broadband connection,
Nmap scan works as it should and only identifies ports that are open.

I ran a packet trace from the Nmap command line while scanning an IP
on the satellite broadband connection, and I received a SYN-ACK for all
ports Nmap scanned.

This is starting to get annoying, and I'm not sure how I can rectify this

Any help on this matter will be dearly appreciated!

I would conjecture that the ISP for the satellite is managing your
connections for you similar to a firewall. In this case, it is trying
to prevent the overhead of managing a TCP connection over the
satellite medium. It would be then plausible that the ISP
automatically SYN ACKs everything. While this behavior would not be
correct, it must work well for their general customer base.

This should be something you take up with the ISP.

-Patrick Donnelly

"Let all men know thee, but no man know thee thoroughly: Men freely
ford that see the shallows."

- Benjamin Franklin

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