Nessus Agents, available with Nessus Manager, alleviate headaches associated with traditional network scanning, like getting credentials, while making it easy to scan a wider array of assets, including ones that are offline.
Most organizations will use a mix of agent-based and agent-less scanning in their Nessus environment. Nessus Agents will be attractive in a number of scenarios, including:
Scanning of laptops or other transient devices that are not always connected to the local network.
Assets that you want or need to scan without credentials.
Assets that you want or need to scan very quickly, for example if you want to immediately scan all your assets for a significant vulnerability like ShellShock.