NMAP Question

Posted on 2008-10-01
Last Modified: 2013-12-04
Hola Experts,

I ran an Nmap scan from and here are the results:

25/tcp open smtp
53/tcp open domain

Only thing is, checked my Pix Firewall and the Inbound acess-list only permits 25. I do not permit DNS into the network, so how is it finding this? and more importantly, how can I find it and shut it off?
Question by:jaysonfranklin
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
LVL 62

Expert Comment

ID: 22617432
It means your PIX is not protecting you. What will you do now?

Author Comment

ID: 22617493
haha u funny.

seriously, if i telnet to port 53 from outside the pix, the port does not appear to be open. so, i was just wondering how the nmap-online found that it was open. it's just confusing since the pix is supposed to be stateful.
LVL 79

Accepted Solution

lrmoore earned 500 total points
ID: 22618163
I believe it to be a false reading by nmap.
It shows mine to also have tcp/53 open and I know for a fact it is not.
Try another online scanner and you will get different results
Or ShieldsUp at

Author Closing Comment

ID: 31502060
thats what figured, i just wondered if somebody out there knew something i didn't. Thanks lrmoore.
LVL 79

Expert Comment

ID: 22618498
Ya, even with an explicit deny acl there are no hits
access-list outside_access_in line 2 extended deny tcp any any eq domain (hitcnt=0)

Yet NMAP still shows it open
53/tcp open domain
80/tcp open http  

HTTP ain't open, either!

I can watch the live log and see the denies on other ports.

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Cisco 2960 unable to add SFP modules to device 9 107
Swapping port on a  Cisco 5510 firewall 1 49
SCSM reports export 1 54
VPN Tunnel Stops Working Cisco RV130W 18 55
I recently attended Cisco Live! in Las Vegas, a conference that boasted over 28,000 techies in attendance, and a week of hands-on learning hosted by a solid partner with which Concerto goes to market.  Every year, Cisco displays cutting-edge technol…
When speed and performance are vital to revenue, companies must have complete confidence in their cloud environment.
Both in life and business – not all partnerships are created equal. As the demand for cloud services increases, so do the number of self-proclaimed cloud partners. Asking the right questions up front in the partnership, will enable both parties …
Both in life and business – not all partnerships are created equal. Spend 30 short minutes with us to learn:   • Key questions to ask when considering a partnership to accelerate your business into the cloud • Pitfalls and mistakes other partners…

697 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question