Where should Nessus scanners be strategically placed within a network topology?

Nessus scanners should not be placed behind a firewall for several reasons. When configured behind a firewall, the scanner may be limited in its ability to effectively identify vulnerabilities across different segments of the network. Firewalls can block various types of traffic, potentially preventing the scanner from accessing systems that need to be assessed. This positioning would restrict the scanner's visibility and could lead to incomplete or inaccurate scanning results, as it wouldn't be able to reach hosts that are behind the firewall.

Furthermore, placing scanners external to the firewall fosters a more thorough assessment of the network perimeter and aids in detecting vulnerabilities that could be exploited from outside. An optimized scan can capture a comprehensive view of both external-facing assets and any potential vulnerabilities in the defense mechanisms.

The strategic placement of Nessus scanners is crucial to ensure they can effectively evaluate all components within the network, especially those that might be exposed to threats from outside. This emphasizes the necessity of having scanners in locations where they can access the maximum number of systems without being obstructed by security devices.