While attempting to discover the remote operating system on the target computer, you receive the following results from an nmap scan:

Starting nmap V. 3.10ALPHA9 ( www.insecure.org/nmap/

<http://www.insecure.org/nmap/> )

Interesting ports on 172.121.12.222:

(The 1592 ports scanned but not shown below are in state: filtered)

Port State Service

21/tcp open ftp

25/tcp open smtp

53/tcp closed domain

80/tcp open http

443/tcp open https

Remote operating system guess: Too many signatures match to reliably

guess the OS.

Nmap run completed — 1 IP address (1 host up) scanned in 277.483

seconds

What should be your next step to identify the OS?

A.
Perform a firewalk with that system as the target IP

B.
Perform a tcp traceroute to the system using port 53

C.
Run an nmap scan with the -v-v option to give a better output

D.
Connect to the active services and review the banner information

Explanation:
Most people don’t care about changing the banners presented by applications listening to open ports and therefore you should get fairly accurate information when grabbing banners from open ports with, for example, a telnet application.