Penetration Testing mailing list archives
Re: All tcp ports open?
From: Chris Brenton <cbrenton () chrisbrenton org>
Date: Mon, 30 Aug 2004 06:37:59 -0400
On Sun, 2004-08-29 at 03:04, Ben Timby wrote:
I am pen-testing a Windows webserver, and a port scan reveals ALL tcp ports open. hping also confirms that a SA is returned for any S packets sent to any port I try.
Been there seen this, its how I like to configure a perimeter. ;-) A number of firewalls will do this if you tweak them right. Gauntlet, iptables, 4.x and prior Firewall-1, and TCPWrapper just to name a few. You can also see this type of response out of load balancers and SYN flood protection devices.
I can connect via netcat any of the ports, and send data, but nothing is returned.
So you complete a TCP three packet handshake, send a single ACK with a payload, and _nothing_ comes back, not even a RST? If so I would lean more towards it being a firewall giving you this response.
In order to verify services, I am required to connect and check for a banner or send appropriate protocol commands to elicit a response.
nmap is your friend: nmap -sT -P0 -A -O -F -oN scan.txt 1.1.1.1/24 "-A" will do some app specific queries to see if there is actually anything listening on the port. I included "-O" because if all the IP's fingerprint exactly the same, its very likely you are talking to a firewall. It sounded like you might be checking only 1 IP address however, in which case you can't compare the fingerprints of different IPs. You can however at least check to see if the fingerprint is for a known firewall that displays the activity you describe. I included "-F" so you are not scanning *every* port. On the up side your scan will go quicker. On the downside, you'll miss apps on non-standard ports. Happy fishing! Chris ------------------------------------------------------------------------------ Ethical Hacking at the InfoSec Institute. All of our class sizes are guaranteed to be 12 students or less to facilitate one-on-one interaction with one of our expert instructors. Check out our Advanced Hacking course, learn to write exploits and attack security infrastructure. Attend a course taught by an expert instructor with years of in-the-field pen testing experience in our state of the art hacking lab. Master the skills of an Ethical Hacker to better assess the security of your organization. http://www.infosecinstitute.com/courses/ethical_hacking_training.html -------------------------------------------------------------------------------
Current thread:
- Re: All tcp ports open?, (continued)
- Re: All tcp ports open? Andres Riancho (Aug 29)
- Re: All tcp ports open? Bill Burge (Aug 29)
- Re: All tcp ports open? dreamwvr () dreamwvr com (Aug 29)
- Re: All tcp ports open? Tim (Aug 29)
- Re: All tcp ports open? Kevin Sheldrake (Aug 29)
- Re: All tcp ports open? Jose Maria Lopez (Aug 29)
- Re: All tcp ports open? Varun Pitale (Aug 29)
- RE: All tcp ports open? Mike Sues (Aug 30)
- Re: All tcp ports open? Jack Burton (Aug 30)
- Re: All tcp ports open? GUsh-T (Aug 30)
- Re: All tcp ports open? Chris Brenton (Aug 30)
- Re: All tcp ports open? Nathan R. Valentine (Aug 30)
- Re: All tcp ports open? sol seclists (Aug 30)
- RE: All tcp ports open? Don Parker (Aug 29)
- RE: All tcp ports open? Meidinger Chris (Aug 30)
- RE: All tcp ports open? Todd Towles (Aug 30)
- Re: All tcp ports open? David M. Zendzian (Aug 30)
- Re: All tcp ports open? Erik Birkholz (Aug 30)
- Re: All tcp ports open? Bill Burge (Aug 31)
- RE: All tcp ports open? Beaty, Bryan (Aug 30)
- RE: All tcp ports open? BĂ©noni MARTIN (Aug 31)
(Thread continues...)