Security Incidents mailing list archives
RE: nmap reveals trinoo_master on router
From: "Dario Ciccarone (dciccaro)" <dciccaro () cisco com>
Date: Wed, 18 Oct 2006 14:32:29 -0400
Hi there: It is always useful to attach the output of a "show tech" from the router under test, and also the command line used while invoking nmap :) I would recommend for you to go and read the nmap documentation - specifically, the "Port scanning basics" section - available at http://insecure.org/nmap/man/man-port-scanning-basics.html. And quoting from said documentation: filtered Nmap cannot determine whether the port is open because packet filtering prevents its probes from reaching the port. The filtering could be from a dedicated firewall device, router rules, or host-based firewall software. These ports frustrate attackers because they provide so little information. Sometimes they respond with ICMP error messages such as type 3 code 13 (destination unreachable: communication administratively prohibited), but filters that simply drop probes without responding are far more common. This forces Nmap to retry several times just in case the probe was dropped due to network congestion rather than filtering. This slows down the scan dramatically. So what nmap is trying to tell you is that, when probing those ports, it got either an ICMP unreachable or nothing at all - ie, instead of getting a SYN+ACK (if the port was open) or a RST (if the port wasn't listening - actuall, if no process was listening on that port) The reason for those ports showing up as 'filtered' is because you have an ACL applied to the external, Internet facing interface on the router - probably blocking those specific ports. You also talk about a PIX firewall behind the router - as we don't know your setup, we have no idea if the router is forwarding all traffic to the firewall, if the router is doing NAT/PAT, etc. Thanks, Dario
-----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of fahimdxb () gmail com Sent: Wednesday, October 18, 2006 7:36 AM To: incidents () securityfocus com Subject: nmap reveals trinoo_master on router On my Cisco Router, I do a nmap scan from outside on the Internet. The result is: " Interesting ports on *.*.50.1: Not shown: 1676 closed ports PORT STATE SERVICE 23/tcp filtered telnet 135/tcp filtered msrpc 1524/tcp filtered ingreslock 27665/tcp filtered Trinoo_Master I am worried about the last two entries. The last nmap was done in Feb this year and I have confirmed that the two port entries (tcp 1524/27665) did not exist then. Though the port state "filtered" is a solace but I am still concerned. How can I be sure that the system has not been compromised? Also the current IOS Version of my Router 2811 is 12.4. It was the same case with open ports when I was using older Router Series 1700 v 12.2, so I thought maybe, it's an IOS issue and I upgraded my Router to 2811 with IOS v 12.4 yesterday. But as soon as I plugged it into the circuit and did a re-scan, I realised the nmap again gives the trinoo_master entry with state as filtered. Where could lie the problem. Is it with my firewall (PIX 515) configuration behind the router? Please Advise!! I have seen Cisco's tech doc that exists here: http://www.cisco.com/en/US/partner/tech/tk59/technologies_whit e_paper09186a0080174a5b.shtml One of the solutions suggested therein is to implement "ip verify unicast reverse-path" on the serial interface, but am not sure what will it serve? Also, I suspect that I had other problems when I gave this command so I reversed it. "sh process cpu" only shows cpu utilisation of about 5-6%. Please advise!! -------------------------------------------------------------- ---------------- This List Sponsored by: Black Hat Attend the Black Hat Briefings & Training USA, July 29-August 3 in Las Vegas. World renowned security experts reveal tomorrow's threats today. Free of vendor pitches, the Briefings are designed to be pragmatic regardless of your security environment. Featuring 36 hands-on training courses and 10 conference tracks, networking opportunities with over 2,500 delegates from 40+ nations. http://www.blackhat.com -------------------------------------------------------------- ----------------
------------------------------------------------------------------------------ This List Sponsored by: Black Hat Attend the Black Hat Briefings & Training USA, July 29-August 3 in Las Vegas. World renowned security experts reveal tomorrow's threats today. Free of vendor pitches, the Briefings are designed to be pragmatic regardless of your security environment. Featuring 36 hands-on training courses and 10 conference tracks, networking opportunities with over 2,500 delegates from 40+ nations. http://www.blackhat.com ------------------------------------------------------------------------------
Current thread:
- nmap reveals trinoo_master on router fahimdxb (Oct 18)
- Re: nmap reveals trinoo_master on router Robin Sheat (Oct 18)
- <Possible follow-ups>
- RE: nmap reveals trinoo_master on router Dario Ciccarone (dciccaro) (Oct 18)
- RE: nmap reveals trinoo_master on router Maxime Ducharme (Oct 23)