List of Well-Known Ports
Port numbers range from 0 to 65535, but only port numbers 0 to 1023 are reserved for privileged services and designated as well-known ports. The following list of well-known port numbers specifies the port used by the server process as its contact port.
Port Number —
|1||TCP Port Service Multiplexer (TCPMUX)|
|5||Remote Job Entry (RJE)|
|18||Message Send Protocol (MSP)|
|20||FTP — Data|
|21||FTP — Control|
|22||SSH Remote Login Protocol|
|25||Simple Mail Transfer Protocol (SMTP)|
|42||Host Name Server (Nameserv)|
|49||Login Host Protocol (Login)|
|53||Domain Name System (DNS)|
|69||Trivial File Transfer Protocol (TFTP)|
|108||SNA Gateway Access Server|
|115||Simple File Transfer Protocol (SFTP)|
|137||NetBIOS Name Service|
|139||NetBIOS Datagram Service|
|143||Interim Mail Access Protocol (IMAP)|
|150||NetBIOS Session Service|
|179||Border Gateway Protocol (BGP)|
|190||Gateway Access Control Protocol (GACP)|
|194||Internet Relay Chat (IRC)|
|197||Directory Location Service (DLS)|
|389||Lightweight Directory Access Protocol (LDAP)|
|396||Novell Netware over IP|
|444||Simple Network Paging Protocol (SNPP)|
- Well-known ports range from 0 through 1023.
- Registered ports are 1024 to 49151.
- Dynamic ports (also called private ports) are 49152 to 65535.
For further information, see RFC 1700.
20: FTP data
21: FTP control port
23: Telnet <= Insecure, not recommended for most uses
43: WHOIS protocol
53: DNS services
67: DHCP server port
68: DHCP client port
80: HTTP traffic <= Normal web traffic
110: POP3 mail port
113: Ident authentication services on IRC networks
143: IMAP mail port
389: LDAP port
443: HTTPS <= Secure web traffic
587: SMTP <= message submission port
631: CUPS printing daemon port
666: DOOM <= This legacy FPS game actually has its own special port
Nmap Cheat Sheet
Nmap Target Selection
|Scan a single IP||nmap 192.168.1.1|
|Scan a host||nmap http://www.testhostname.com|
|Scan a range of IPs||nmap 192.168.1.1-20|
|Scan a subnet||nmap 192.168.1.0/24|
|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 22 192.168.1.1|
|Scan a range of ports||nmap -p 1-100 192.168.1.1|
|Scan 100 most common ports (Fast)||nmap -F 192.168.1.1|
|Scan all 65535 ports||nmap -p- 192.168.1.1|
Nmap Port Scan types
|Scan using TCP connect||nmap -sT 192.168.1.1|
|Scan using TCP SYN scan (default)||nmap -sS 192.168.1.1|
|Scan UDP ports||nmap -sU -p 123,161,162 192.168.1.1|
|Scan selected ports – ignore discovery||nmap -Pn -F 192.168.1.1|
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.
Take a look at the Nmap Tutorial for a detailed look at the scan process.
Service and OS Detection
|Detect OS and Services||nmap -A 192.168.1.1|
|Standard service detection||nmap -sV 192.168.1.1|
|More aggressive Service Detection||nmap -sV –version-intensity 5 192.168.1.1|
|Lighter banner grabbing detection||nmap -sV –version-intensity 0 192.168.1.1|
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 192.168.1.1|
|Save results as XML||nmap -oX outputfile.xml 192.168.1.1|
|Save results in a format for grep||nmap -oG outputfile.txt 192.168.1.1|
|Save in all formats||nmap -oA outputfile 192.168.1.1|
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 192.168.1.1|
|Get help for a script||nmap –script-help=ssl-heartbleed|
|Scan using a specific NSE script||nmap -sV -p 443 –script=ssl-heartbleed.nse 192.168.1.1|
|Scan with a set of scripts||nmap -sV –script=smb* 192.168.1.1|
According to my Nmap install there are currently 581 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.
--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 192.168.1.0/24|
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 192.168.1.0/24|
|Get HTTP headers of web services||nmap –script=http-headers 192.168.1.0/24|
|Find web apps from known paths||nmap –script=http-enum 192.168.1.0/24|
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 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 192.168.1.0/24|
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 192.168.1.0/24|
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 IP address and DNS lookups.
Testing your network perimeter from an external perspective is key when you wish to get the most accurate results. By assessing your exposure from the attackers perspective you can validate firewall rule audits and understand exactly what is allowed into your network. This is the reason we offer a hosted or online version of the Nmap port scanner. To enable remote scanning easily and effectively because anyone who has played with
shodan.io knows very well how badly people test their perimeter networks.