Port scanning


The Network Mapper - Free Security Scanner Nmap

Common options



Port ranges (default: most common 1000 ports), -p- all ports (1-65536)


Version scanning, enforces full TCP connection


Script scanning


OS detection


Aggressive scan options, combines: -O, -sV, -sC, --traceroute


Set timing template (higher is faster), aka paranoid|sneaky|polite|normal|aggressive|insane (default: 3, aka normal)


Basename (Output to all formats)


UDP scan


Skip host discovery, use this option if the host is blocking ping probes.

-v -vv

Increase verbosity

-d -dd

Debug, even more verbose


set to 1 or 0 to considerably speed up scan (but gets a bit less accurate)

Note: There are a ton of other options, like more exotic scan types, spoofing IP or MAC addresses, etc.


Note: Nmap can only perform TCP SYN scans (-sS), when running as privileged user (root or sudoer), otherwise it falls back to full TCP 3-way handshakes (-sT) per default.


Light scan

sudo nmap --top-ports 10 --open -oA nmap_light <ip>

Default scan

sudo nmap -sV -oA nmap_default <ip>

Heavy scan

sudo nmap -p- -sV -sC --reason -oA nmap_heavy <ip>

Scan for "safe" vulns

sudo nmap --script "vuln and safe" -oA nmap_vuln <ip>

Scan for SMB vulns

sudo nmap -p 139,445 --script smb-vuln*  -oA nmap_vuln_smb <ip>


sudo nmap -sU -oA nmap_udp <ip>

Useful stuff

Get open ports comma separated

grep -oP '\d{1,5}/open' nmap.gnmap | cut -d  "/" -f 1 | paste -s -d ','

Nmap scripts

Quicker scanning and smarter identification

GitHub - scan-tools/banner-plus.nse


NSE script based on Vulners.com API

GitHub - vulnersCom/nmap-vulners


A script that you can run in the background!

GitHub - 21y4d/nmapAutomator

./nmapAutomator <ip> All

netcat (nc)

TCP/IP swiss army knife

The GNU Netcat -- Official homepage


Connect scan (only validates if ports are open)

nc -nvv -w 1 -z <ip> <port-range>


nc -nv -u -z -w 1 <ip> <port-range>

No response means port is open, otherwise a ICMP packet port unreachable is sent back. BUT: Response may get dropped (firewalls, routers, ...) -> false positive

Port knocking

In computer networking, port knocking is a method of externally opening ports on a firewall by generating a connection attempt on a set of prespecified closed ports.

-- Wikipedia


Actually knock to a port

nmap -Pn -sT --host_timeout 201 --max-retries 0 -p <port> <ip>


echo "" > /dev/tcp/<ip>/<port>

Simple bash port scanner

for i in {1..65535}; do (echo > /dev/tcp/<ip>/$i) >/dev/null 2>&1 && echo $i is open; done

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