📱 Mobile Security Tips
Sarah Chen — iOS Security Specialist
What is Nmap?
Nmap (Network Mapper) is an open-source tool for network discovery and security auditing. It is widely used in penetration testing, network inventory, managing service upgrade schedules, and monitoring host or service uptime.
Installation
Nmap is available on various platforms:
- On Linux, you can install it using your distribution’s package manager:
sudo apt-get install nmap # Debian/Ubuntu
sudo dnf install nmap # Fedora
sudo yum install nmap # RHEL/CentOS
brew install nmap
Basic Syntax
The basic syntax for Nmap is:
nmap [options] {target}
Discovery
Use these commands to discover active hosts and services.
Ping Scan
nmap -sn 192.168.1.0/24
This command performs a ping scan to find live hosts in the subnet.
Service Version Detection
nmap -sV 192.168.1.10
Detects the service version running on open ports.
Scanning
Basic Scan
nmap 192.168.1.10
This performs a simple scan of the specified target.
Scanning Specific Ports
nmap -p 80,443 192.168.1.10
This scans only ports 80 and 443.
Exploitation
OS Detection
nmap -O 192.168.1.10
This attempts to determine the operating system of the target.
Aggressive Scan
nmap -A 192.168.1.10
This performs an aggressive scan to enable OS detection, version detection, script scanning, and traceroute.
Analysis
Scripting
nmap --script vuln 192.168.1.10
This runs vulnerability detection scripts against the target.
Output Formats
nmap -oX output.xml 192.168.1.10
Outputs the scan results in XML format for further analysis.
Evasion
Fragmentation
nmap -f 192.168.1.10
This fragments packets to evade detection.
Timing Options
nmap -T4 192.168.1.10
This sets the timing template for faster scans.
Reporting
Saving Your Scan
nmap -oN scan.txt 192.168.1.10
This saves a normal output of the scan results to a text file.
Quick Reference Table
| Flag | Description |
|---|---|
| -sn | Ping scan (no port scan) |
| -sV | Service version detection |
| -O | OS detection |
| -A | Aggressive scan |
| –script | Script scanning |
| -oX | XML output |
| -f | Fragment packets |
| -T | Set timing template |
| -oN | Normal output |
Pro Tips
- Combine options: You can combine multiple flags, e.g.,
nmap -sV -O -A 192.168.1.10for a comprehensive output. - Use
nmap -vto increase verbosity of the output for more details. - Schedule regular scans using cron jobs for continuous monitoring.
Real-World Examples
Scenario: Network Audit
nmap -sS -T4 -p- -oA audit_report 192.168.1.0/24
This will perform a stealth SYN scan for all ports against the specified network and save the output in all formats.
Scenario: Web Server Test
nmap -p 80,443 --script http-enum 192.168.1.10
This scans the web server for vulnerabilities related to the HTTP services running.