Steve Salisbury
Agentless Scanning
In this article:


The quest for seamless, efficient, and comprehensive scanning solutions has never been more critical. As organizations juggle a multitude of devices, servers, and applications across various platforms, the traditional approach of deploying software agents for scanning can become cumbersome and resource-intensive. Agentless scanning provides a streamlined alternative that is rapidly gaining traction for its agility and reduced footprint.

Runecast has been at the forefront of agentless scanning technology, successfully implementing it for AWS, Azure, GCP, Kubernetes, and VMware environments in previous versions. Taking a groundbreaking step forward, Runecast now introduces a first in the industry: agentless scanning capabilities for Windows and Linux operating systems in your VMware infrastructure.

What is Agentless Scanning?

Agentless scanning refers to a method of monitoring computer networks, systems, and applications without requiring the installation of software agents on each target host to be scanned.

Agentless scanning typically relies on existing protocols and services available on network devices, servers, or applications to collect performance data. Common methods and protocols used in agentless scanning include:

  1. Simple Network Management Protocol (SNMP): Used for collecting information about network devices such as routers, switches, printers, and some servers.
  2. Windows Management Instrumentation (WMI): Used for the monitoring and management of Windows-based systems.
  3. Common Information Model (CIM): An open standard that allows for the collection of data from a variety of hardware and software components.
  4. Remote Monitoring (RMON): Used to scan network operational activities through remote devices known as probes or monitors.
  5. Syslog: Used to collect log and event data from different types of systems and devices.
  6. Secure Shell (SSH): Used for executing commands and reading the results on Unix/Linux systems.
  7. Windows Remote Management (WinRM): A Windows-based protocol that allows for remote management of hardware and software.
  8. APIs: Application Programming Interfaces provided by applications for monitoring and management.

Advantages of Agentless Monitoring 

1.  Simplicity: Since there's no need to install, maintain, or update agents on each target system, deployment is straightforward. This is particularly useful for organizations with diverse environments.

2.  Lower Overhead: Agentless solutions consume fewer resources on the target system because they don't run constantly in the background. This minimizes performance impacts on the scanned systems.

3.  No Persistent Footprint: Without permanent agents, there's no risk of the agents becoming outdated or corrupted.

4.  Rapid Deployment: Agentless solutions can be quickly rolled out across the environment, allowing for faster responses to emerging threats or compliance needs.

5.  Fewer Compatibility Issues: Without the need for an agent, there's less worry about software compatibility issues or conflicts with other applications.

6.  Reduced Maintenance: Without agents, there's no need for regular updates or patches on the target systems. This can save time and reduce potential issues that could arise during updates.

7.  Flexibility: Agentless scanning can be more adaptable to varied IT environments. For instance, you can easily scan a system that is only occasionally connected to the network.

8.  Reduced Attack Surface: Since there are no agents permanently installed on the target system, there's one less potential avenue for attackers to exploit.

9.  Scalability: Agentless solutions are easier to scale, especially in dynamic or cloud environments where the number and type of instances can change rapidly.

Runecast and Secure Agentless Scanning for OS

Beginning with version 6.8 (released 7 November 2023), Runecast introduces the capability for secure agentless scanning of vSphere workloads. This new scanning method allows for the assessment of vulnerabilities in operating systems hosted on vSphere virtual machines without the need for installing agents, using additional credentials, or relying on VMware tools.

This enhancement provides a more streamlined and non-invasive monitoring approach that diminishes the typical demands of maintenance and deployment time, while also minimizing the potential points of vulnerability in your network environment.

Leveraging the innovative Runecast Scanner appliance, Runecast utilizes VMware's snapshot functionality to conduct the OS analyses. It securely retains the analysis results within the Runecast platform and subsequently removes the snapshots to conserve critical resources. 

Once deployed within your vSphere environment, the Runecast Scanner operates securely, with a strict assurance that no data is transferred outside of your data center.


The introduction of agentless scanning for operating systems reflects Runecast's dedication to technological innovation and delivering superior solutions to our customers. With the growing trend toward simpler, less-invasive monitoring methods, Runecast is at the forefront of adopting agentless scanning.

As the technology of agentless scanning advances and refines, it is set to become an ever more critical instrument in the arsenal of IT security management. This method streamlines the process by eliminating the time required for deployment and upkeep of agents and simultaneously reduces the potential vectors for security breaches in environments.

Organizations that embrace the agentless methodology stand to gain from a reduction in resource usage, diminished compatibility complications, and enhanced scalability. This shift affords administrators more time to focus on fortifying their environments, aiding in achieving the coveted goal of 99.9999% uptime.

Meet other Runecasters here:

Unlock the Power of Secure Agentless Scanning for OS

Get Free Trial