Hi Faisal,
I found that using nmap alone is usually enough, provided you use the
proper settings. An exception is when you're dealing with a firewall
trying to assess how exactly things interconnect, in such cases you can
try hping2/3 or firewalk.
A short time ago I posted an answer somewhere about the most useful nmap
settings to scan a "normal" network. IMHO:
* use a very comon source port, like 80 (-g 80)
* fragment, and be sure that nothing on YOUR side is trying to defragment
(-f)
* use paranoid timing, to avoid overreaction from an eventual IDS (-T0)
* use SYN scan (-sS)
* use decoys if overreacting IDS are a concern, and if allowed by your
contract! (-D {decoy1},{decoy2},...)
Then go for any advanced techniques, as required (for example ACK or
Window scan).
You can combine OS detection to the above, scan UDP ports, etc., this will
depend exactly on the setup of the network you're checking, and what are
you looking for.
If you don't know what to expect, scan the entire port range, sometimes I
found interesting things in high ports (for example a proxy, or a Java
application server), that were not supposed to be open to the world.
Lastly, don't forget some of the most esoteric and advanced techniques,
that are used once every solsctice, like IPID scan from probably trusted
machines, etc.
Because some times you need to use advanced techniques, very often you
need to scan more than once, but I also recommend (if possible) to scan
from a completely different source IP address (example: scanning a certain
system in Spain from my country showed 2 open ports of a proxy installed
by the ISP, but these ports were not shown when scanned from the same
ISP's network).
IMHO nmap is simply the best port scanner out there. But of course other
people can have different preferences, so no flame wars on port scanners
please ;-)
I like it on Linux more than on Windows, *somehow* I found it more
reliable ;-)
IIRC, Fyodor is a member of this list, so perhaps he can enlighten us all
(or send us to RTFM ;-)
Cheers,
Miguel Dilaj (Nekromancer)
Vice-President of IT Security Research, OISSG
Faisal Khan <faisal@netxs.com.pk>
13/12/2004 14:46
To: pen-test@securityfocus.com
cc: (bcc: Miguel Dilaj/PH/Novartis)
Subject: Port Scanning.
What's a good industry practise whilst doing port-scanning during a
pen-test.
Do you rely on the results of a single vendor's software or do you use
multiple softwares?
Also, with each OEM/vendor - do you scan once or twice?
I need to do a scan on a Class C Address if that matters in any way.
Faisal
