Network vulnerability scanning is the automated assessment of network-connected systems, including servers, workstations, routers, switches, firewalls, and other devices, to identify known security weaknesses. A network vulnerability scanner discovers live hosts across defined IP ranges, identifies open ports and running services, and checks them for issues such as unpatched software, outdated protocols, weak encryption, default credentials, and insecure configurations, then reports each finding with a severity rating.
Network scans are typically run from two vantage points. External scans assess internet-facing systems from an attacker’s perspective outside the perimeter, while internal scans assess systems from inside the network to reveal what an attacker or malicious insider could reach after gaining a foothold. Both are commonly required by compliance frameworks such as PCI DSS. Because networks change frequently as devices are added, reconfigured, or decommissioned, scanning should run on a regular cadence and after significant changes, with results validated and tracked through to remediation.