Network Security
Network Scanning & Reconnaissance
Before securing or attacking a network, you first need to know what's actually on it.
Network scanning tools send probe traffic to a range of addresses and
report what responds, live hosts, open ports, sometimes even the software version running
behind a port. nmap is the standard open-source tool for this.
# Scan a network range for live hosts and open ports
nmap -sV 192.168.1.0/24
# Scan a single host more thoroughly
nmap -A 192.168.1.14nmap reports which hosts on that range responded, which ports are open on each, and (with -sV) its best guess at what software/version is listening on each port. A penetration tester runs this to find what's reachable before testing it further. A defender runs the exact same command against their own network, to spot anything exposed that shouldn't be.