Open Port Scanning and OS Detection with Nmap in Kali Linux

In this tutorial we are going to use Nmap in Kali Linux to scan for open ports scan and we will be using OS detection. Nmap stands for Network Mapper and is an open source tool for network exploration and security auditing which comes standard with Kali Linux but is also available for Windows, OSX and many other UNIX platforms. Nmap also has a graphical user interface called Zenmap.

First I want to start off with a little warning: Please be careful using the more aggressive functions of Nmap against hosts you do not own or do not have permission to scan. It may be against your ISP’s terms to use some Nmap features.

Open Port Scanning and OS Detection

Let’s start with a ping scan on an IP range to determine live hosts using the following command:

nmap -sP 192.168.0.0-100

Next we will start a SYN scan with OS detection on one of the live hosts using the following command:

nmap -sS [ip address]-O

Now we will start an open port scan with version detection using the following command:

nmap -sV 192.168.0.1 -A

When we add -v to the command we can increase the verbosity :
nmap -sV 192.168.0.13 -A -v

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Nmap options summary

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
–exclude-ports <port ranges>: Exclude the specified ports from scanning
-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-args-file=filename: provide NSE script args in a file
–script-trace: Show all data sent and received
–script-updatedb: Update the script database.
–script-help=<Lua scripts>: Show help about scripts.
<Lua scripts> is a comma-separated list of script-files or
script-categories.

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
–proxies <url1,[url2],…>: Relay connections through HTTP/SOCKS4 proxies
–data <hex string>: Append a custom payload to sent packets
–data-string <string>: Append a custom ASCII string to sent packets
–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

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