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sec-notes/network/nmap.md
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---
title: "Nmap"
description: "Host discovery, port scanning, service detection and NSE scripting"
tags: ["nmap", "network", "enumeration"]
publishDate: 2026-05-18
---
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
- [Host Discovery](#host-discovery)
- [Port Scanning](#port-scanning)
- [Service & Version Detection](#service--version-detection)
- [OS Detection](#os-detection)
- [Aggressive Scan](#aggressive-scan)
- [Timing Templates](#timing-templates)
- [NSE Scripts](#nse-scripts)
- [Output Formats](#output-formats)
- [Common Profiles](#common-profiles)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
Nmap is a network scanner used for host discovery, port scanning, service/version detection, OS fingerprinting, and vulnerability scripting via NSE.
## Host Discovery
```bash
nmap -sn 192.168.1.0/24 # ping sweep, no port scan
nmap -sn -PR 192.168.1.0/24 # ARP ping (local network)
nmap -Pn $IP # skip host discovery, treat as up
```
## Port Scanning
```bash
nmap $IP # top 1000 ports (SYN scan if root)
nmap -p 80,443,8080 $IP # specific ports
nmap -p 1-65535 $IP # all ports
nmap -p- $IP # shorthand for all ports
nmap -sU $IP # UDP scan
nmap -sU -sS $IP # UDP + SYN together
```
Scan types:
- `-sS`: SYN scan (stealth, requires root)
- `-sT`: TCP connect scan (no root needed)
- `-sU`: UDP scan
- `-sA`: ACK scan (firewall rule mapping)
- `-sN/sF/sX`: Null, FIN, Xmas (evasion, unreliable on Windows)
## Service & Version Detection
```bash
nmap -sV $IP
nmap -sV --version-intensity 9 $IP # more aggressive probing
```
## OS Detection
```bash
nmap -O $IP
nmap -O --osscan-guess $IP # guess if not confident
```
## Aggressive Scan
```bash
nmap -A $IP # -sV -O --script=default --traceroute
```
## Timing Templates
```bash
nmap -T0 $IP # paranoid (IDS evasion, very slow)
nmap -T1 $IP # sneaky
nmap -T3 $IP # normal (default)
nmap -T4 $IP # aggressive (faster, good for CTFs)
nmap -T5 $IP # insane (may miss results)
```
## NSE Scripts
```bash
nmap --script default $IP
nmap --script vuln $IP
nmap --script "ftp-*" $IP
nmap --script safe $IP
nmap --script $script --script-args user=$user,pass=$password $IP
```
Common script categories: `auth`, `brute`, `default`, `discovery`, `dos`, `exploit`, `intrusive`, `safe`, `version`, `vuln`.
Scripts are located in `/usr/share/nmap/scripts/`.
## Output Formats
```bash
nmap -oN output.txt $IP # normal
nmap -oX output.xml $IP # XML
nmap -oG output.gnmap $IP # grepable
nmap -oA output $IP # all three at once
```
## Common Profiles
Quick full scan:
```bash
nmap -p- -T4 --min-rate 5000 -sV -sC -oA full $IP
```
CTF/lab initial recon:
```bash
nmap -sV -sC -p- --open $IP
```
UDP top ports:
```bash
nmap -sU --top-ports 100 $IP
```