Nmap cheat sheet

Here is a compliation of the best Nmap cheat sheet

Nmap Target Selection
Scan a single IP    nmap
Scan a host    nmap www.testhostname.com
Scan a range of IPs    nmap
Scan a subnet    nmap
Scan targets from a text file    nmap -iL list-of-ips.txt

These are all default scans, which will scan 1000 TCP ports. Host discovery will take place.

Nmap Port Selection
Scan a single Port    nmap -p 22
Scan a range of ports    nmap -p 1-100
Scan 100 most common ports (Fast)    nmap -F
Scan all 65535 ports    nmap -p-

Nmap Port Scan types
Scan using TCP connect    nmap -sT
Scan using TCP SYN scan (default)    nmap -sS
Scan UDP ports    nmap -sU -p 123,161,162
Scan selected ports – ignore discovery    nmap -Pn -F

Privileged access is required to perform the default SYN scans. If privileges are insufficient a TCP connect scan will be used. A TCP connect requires a full TCP connection to be established and therefore is a slower scan. Ignoring discovery is often required as many firewalls or hosts will not respond to PING, so could be missed unless you select the -Pn parameter. Of course this can make scan times much longer as you could end up sending scan probes to hosts that are not there.

Service and OS Detection
Detect OS and Services    nmap -A
Standard service detection    nmap -sV
More aggressive Service Detection    nmap -sV –version-intensity 5
Lighter banner grabbing detection    nmap -sV –version-intensity 0

Service and OS detection rely on different methods to determine the operating system or service running on a particular port. The more aggressive service detection is often helpful if there are services running on unusual ports. On the other hand the lighter version of the service will be much faster as it does not really attempt to detect the service simply grabbing the banner of the open service.

Nmap Output Formats
Save default output to file    nmap -oN outputfile.txt
Save results as XML    nmap -oX outputfile.xml
Save results in a format for grep    nmap -oG outputfile.txt
Save in all formats    nmap -oA outputfile

The default format could also be saved to a file using a simple file redirect command > file. Using the -oN option allows the results to be saved but also can be monitored in the terminal as the scan is under way.

Digging deeper with NSE Scripts
Scan using default safe scripts    nmap -sV -sC
Get help for a script    nmap –script-help=ssl-heartbleed
Scan using a specific NSE script    nmap -sV -p 443 –script=ssl-heartbleed.nse
Scan with a set of scripts    nmap -sV –script=smb*

According to my Nmap install there are currently 471 NSE scripts. The scripts are able to perform a wide range of security related testing and discovery functions. If you are serious about your network scanning you really should take the time to get familiar with some of them.

The option –script-help=$scriptname will display help for the individual scripts. To get an easy list of the installed scripts try locate nse | grep script.

You will notice I have used the -sV service detection parameter. Generally most NSE scripts will be more effective and you will get better coverage by including service detection.

A scan to search for DDOS reflection UDP services
Scan for UDP DDOS reflectors    nmap –sU –A –PN –n –pU:19,53,123,161 –script=ntp-monlist,dns-recursion,snmp-sysdescr

UDP based DDOS reflection attacks are a common problem that network defenders come up against. This is a handy Nmap command that will scan a target list for systems with open UDP services that allow these attacks to take place. Full details of the command and the background can be found on the Sans Institute Blog where it was first posted.

HTTP Service Information
Gather page titles from HTTP services    nmap –script=http-title
Get HTTP headers of web services    nmap –script=http-headers
Find web apps from known paths    nmap –script=http-enum

There are many HTTP information gathering scripts, here are a few that are simple but helpful when examining larger networks. Helps in quickly identifying what the HTTP service is that is running on the open port. Note the http-enum script is particularly noisy. It is similar to Nikto in that it will attempt to enumerate known paths of web applications and scripts. This will inevitably generated hundreds of 404 HTTP responses in the web server error and access logs.

Detect Heartbleed SSL Vulnerability
Heartbleed Testing    nmap -sV -p 443 –script=ssl-heartbleed

Heartbleed detection is one of the available SSL scripts. It will detect the presence of the well known Heartbleed vulnerability in SSL services. Specify alternative ports to test SSL on mail and other protocols (Requires Nmap 6.46).

IP Address information
Find Information about IP address    nmap –script=asn-query,whois,ip-geolocation-maxmind

Gather information related to the IP address and netblock owner of the IP address. Uses ASN, whois and geoip location lookups. See the IP Tools for more information and similar online queries.

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