NMAP

Nmap is typically utilised for network mapping, enumeration and security auditing. It can scan large networks extremely quickly and reliably and scales well from a single host to a class A network, (that may take a while though!). Nmap enumerates what hosts are alive on a network, their open ports and consequently the services/applications they are running.  From this information nmap can also attempt to fingerprint the OS in use on the remote host.  Another use is gleaning information on firewall rulesets which may help you further in a VA/Penetration Test type scenario. 

It is available from insecure.org

Installation:

Requires Winpcap (included)

Just extract the version you want dependant on your OS i.e. nmap-VERSION-win32.zip file into an appropriate directory, tar -zxvf the appropriate nmap tarball or for simplicity and upgrade, use the rpm or apt-get facility. 

Command Syntax:

Nmap 5.51 ( http://nmap.org )
Usage: nmap [Scan Type(s)] [Options] {target specification}
 

TARGET SPECIFICATION:
Can pass hostnames, IP addresses, networks, etc.
Ex: scanme.nmap.org, microsoft.com/24, 192.168.0.1; 10.0.0-255.1-254
-iL <inputfilename>: Input from list of hosts/networks
-iR <num hosts>: Choose random targets
--exclude <host1[,host2][,host3],...>: Exclude hosts/networks
--excludefile <exclude_file>: Exclude list from file
 

HOST DISCOVERY:
-sL: List Scan - simply list targets to scan
-sn: Ping Scan - disable port scan
-Pn: Treat all hosts as online -- skip host discovery
-PS/PA/PU/PY[portlist]: TCP SYN/ACK, UDP or SCTP discovery to given ports
-PE/PP/PM: ICMP echo, timestamp, and netmask request discovery probes
-PO[protocol list]: IP Protocol Ping
-n/-R: Never do DNS resolution/Always resolve [default: sometimes]
--dns-servers <serv1[,serv2],...>: Specify custom DNS servers
--system-dns: Use OS's DNS resolver
--traceroute: Trace hop path to each host
 

SCAN TECHNIQUES:
-sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
-sU: UDP Scan
-sN/sF/sX: TCP Null, FIN, and Xmas scans
--scanflags <flags>: Customize TCP scan flags
-sI <zombie host[:probeport]>: Idle scan
-sY/sZ: SCTP INIT/COOKIE-ECHO scans
-sO: IP protocol scan
-b <FTP relay host>: FTP bounce scan
 

PORT SPECIFICATION AND SCAN ORDER:
-p <port ranges>: Only scan specified ports
Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080,S:9
-F: Fast mode - Scan fewer ports than the default scan
-r: Scan ports consecutively - don't randomize
--top-ports <number>: Scan <number> most common ports
--port-ratio <ratio>: Scan ports more common than <ratio>
 

SERVICE/VERSION DETECTION:
-sV: Probe open ports to determine service/version info
--version-intensity <level>: Set from 0 (light) to 9 (try all probes)
--version-light: Limit to most likely probes (intensity 2)
--version-all: Try every single probe (intensity 9)
--version-trace: Show detailed version scan activity (for debugging)
 

SCRIPT SCAN:
-sC: equivalent to --script=default
--script=<Lua scripts>: <Lua scripts> is a comma separated list of
directories, script-files or script-categories
--script-args=<n1=v1,[n2=v2,...]>: provide arguments to scripts
--script-trace: Show all data sent and received
--script-updatedb: Update the script database.
 

OS DETECTION:
-O: Enable OS detection
--osscan-limit: Limit OS detection to promising targets
--osscan-guess: Guess OS more aggressively
 

TIMING AND PERFORMANCE:
Options which take <time> are in seconds, or append 'ms' (milliseconds),
's' (seconds), 'm' (minutes), or 'h' (hours) to the value (e.g. 30m).
-T<0-5>: Set timing template (higher is faster)
--min-hostgroup/max-hostgroup <size>: Parallel host scan group sizes
--min-parallelism/max-parallelism <numprobes>: Probe parallelization
--min-rtt-timeout/max-rtt-timeout/initial-rtt-timeout <time>: Specifies
probe round trip time.
--max-retries <tries>: Caps number of port scan probe retransmissions.
--host-timeout <time>: Give up on target after this long
--scan-delay/--max-scan-delay <time>: Adjust delay between probes
--min-rate <number>: Send packets no slower than <number> per second
--max-rate <number>: Send packets no faster than <number> per second
 

FIREWALL/IDS EVASION AND SPOOFING:
-f; --mtu <val>: fragment packets (optionally w/given MTU)
-D <decoy1,decoy2[,ME],...>: Cloak a scan with decoys
-S <IP_Address>: Spoof source address
-e <iface>: Use specified interface
-g/--source-port <portnum>: Use given port number
--data-length <num>: Append random data to sent packets
--ip-options <options>: Send packets with specified ip options
--ttl <val>: Set IP time-to-live field
--spoof-mac <mac address/prefix/vendor name>: Spoof your MAC address
--badsum: Send packets with a bogus TCP/UDP/SCTP checksum
 

OUTPUT:
-oN/-oX/-oS/-oG <file>: Output scan in normal, XML, s|<rIpt kIddi3,
and Grepable format, respectively, to the given filename.
-oA <basename>: Output in the three major formats at once
-v: Increase verbosity level (use -vv or more for greater effect)
-d: Increase debugging level (use -dd or more for greater effect)
--reason: Display the reason a port is in a particular state
--open: Only show open (or possibly open) ports
--packet-trace: Show all packets sent and received
--iflist: Print host interfaces and routes (for debugging)
--log-errors: Log errors/warnings to the normal-format output file
--append-output: Append to rather than clobber specified output files
--resume <filename>: Resume an aborted scan
--stylesheet <path/URL>: XSL stylesheet to transform XML output to HTML
--webxml: Reference stylesheet from Nmap.Org for more portable XML
--no-stylesheet: Prevent associating of XSL stylesheet w/XML output
 

MISC:
-6: Enable IPv6 scanning
-A: Enable OS detection, version detection, script scanning, and traceroute
--datadir <dirname>: Specify custom Nmap data file location
--send-eth/--send-ip: Send using raw ethernet frames or IP packets
--privileged: Assume that the user is fully privileged
--unprivileged: Assume the user lacks raw socket privileges
-V: Print version number
-h: Print this help summary page.

 

C:\Users\dell>nmap -sC -O -p 1-1024 213.179.200.200

Starting Nmap 5.50 ( http://nmap.org ) at 2011-04-29 08:36 GMT Daylight Time
Stats: 0:00:12 elapsed; 0 hosts completed (1 up), 1 undergoing Script Scan
NSE Timing: About 0.00% done
Nmap scan report for server213-179-200-200.livedns.org.uk (213.179.200.200)
Host is up (0.035s latency).
Not shown: 1023 filtered ports
PORT STATE SERVICE
80/tcp open http
|_http-methods: No Allow or Public header in OPTIONS response (status code 200)
|_http-title: Site Not Found
Warning: OSScan results may be unreliable because we could not find at least 1 o
pen and 1 closed port
Device type: switch|WAP
Running (JUST GUESSING): HP embedded (95%), D-Link embedded (88%), TRENDnet embe
dded (88%)
Aggressive OS guesses: HP 4000M ProCurve switch (J4121A) (95%), D-Link DWL-624+
or DWL-2000AP, or TRENDnet TEW-432BRP WAP (88%)
No exact OS matches for host (test conditions non-ideal).

OS detection performed. Please report any incorrect results at http://nmap.org/s
ubmit/ .
Nmap done: 1 IP address (1 host up) scanned in 17.02 seconds

C:\nmap>nmap -A -p- 200.100.100.234

Starting Nmap 5.50 ( http://nmap.org ) at 2011-04-29 08:36 GMT Daylight Time
Interesting ports on 200.100.100.234:
(The 65530 ports scanned but not shown below are in state: closed)
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 3.6.1p2 (protocol 1.99)
111/tcp open rpcbind 2 (rpc #100000)
139/tcp open netbios-ssn Samba smbd 3.X (workgroup: WORKGROUP)
445/tcp open netbios-ssn Samba smbd 3.X (workgroup: WORKGROUP)
1241/tcp open ssl Nessus security scanner
MAC Address: 00:0C:29:2A:CF:F9 (VMware)
Device type: general purpose
Running: Linux 2.4.X|2.5.X
OS details: Linux 2.4.0 - 2.5.20

Nmap finished: 1 IP address (1 host up) scanned in 21.611 seconds

Zenmap is the new GUI packages with nmap and this can be used instead of the command line option.