Certified: The Security+ Prepcast

In our last episode, we explored two foundational tools in the world of security monitoring—Security Content Automation Protocol and security benchmarks. These tools help standardize and enforce the way organizations assess systems and measure compliance. In this episode, we continue our exploration of security monitoring tools by focusing on two practical and widely used methods: agent-based versus agentless monitoring, and Security Information and Event Management systems. Understanding how these tools work—and where they excel—will help you build smarter, more responsive security operations.
Let’s begin with agent-based and agentless monitoring. These two methods describe how monitoring tools collect data from systems, applications, and networks. Each has advantages and trade-offs, and many organizations use a combination of both.
Agent-based monitoring means that a small software program—called an agent—is installed directly on the system being monitored. This agent collects detailed information about system performance, application behavior, file activity, and security events. The data is then sent to a central monitoring server for analysis.
The primary advantage of agent-based monitoring is depth. Because the agent has direct access to the system, it can gather rich, granular data—such as process lists, file hashes, registry changes, or kernel-level events. This level of detail is especially important for endpoint detection, forensic investigation, and behavioral analysis. Agent-based tools can also work across different operating systems and platforms, including cloud environments and mobile devices.
However, agents come with some challenges. First, they must be installed and maintained. In large environments, this means managing software deployment, updates, and compatibility. Second, agents consume resources. While most are lightweight, they still use CPU, memory, and bandwidth. In high-performance systems or resource-constrained devices, this overhead may be a concern. Lastly, agents must be secured. If an attacker compromises an agent, they may gain insight into your monitoring strategy—or attempt to disable it.
Now let’s contrast this with agentless monitoring. Agentless tools do not require software to be installed on the monitored device. Instead, they collect data remotely using standard protocols and interfaces—such as Secure Shell, Windows Management Instrumentation, Simple Network Management Protocol, or application programming interfaces. This approach is often faster to deploy, easier to maintain, and less intrusive.
Agentless monitoring is ideal for quick visibility, compliance checks, or infrastructure health monitoring. For example, a network team might use agentless tools to query switches and routers for uptime, bandwidth usage, or interface errors. A compliance team might use agentless scans to check patch levels across endpoints without deploying new software.
But agentless tools also have limitations. Because they do not run locally, they often have less access to low-level data. They may miss transient processes, subtle file changes, or advanced threats that only reveal themselves at the endpoint level. Agentless tools also rely on network connectivity and correct configurations. If ports are blocked, credentials are outdated, or interfaces are disabled, the tool may fail to collect accurate data.
Let’s consider a real-world comparison. A financial institution wants to monitor its workstations for signs of insider threats. They deploy an agent-based solution that records login attempts, file access, and process execution in real time. The agents detect when a user copies large amounts of data to a USB drive—something agentless tools might miss. At the same time, the institution uses agentless scanners to check server patch levels every week. This approach balances deep visibility with operational efficiency.
In another example, a hospital installs agents on its patient data servers to monitor for unauthorized access, while using agentless monitoring to watch network devices for outages and configuration drift. This hybrid approach allows them to tailor the tool to the environment—using agents where depth is critical and agentless monitoring where breadth and speed are more important.
In short, agent-based monitoring gives you a microscope—high detail, close range, but with management requirements. Agentless monitoring gives you a wide-angle lens—faster and easier to deploy, but with less depth. Each has a place, and the right tool depends on your goals, infrastructure, and risk tolerance.
Now let’s move to the second half of this episode—Security Information and Event Management, often abbreviated as S I E M. A Security Information and Event Management system is a centralized platform that collects, aggregates, correlates, and analyzes security events from across the environment. It is one of the most important tools in a modern security operations center.
The role of a Security Information and Event Management system is to bring together data from diverse sources—firewalls, endpoint agents, intrusion detection systems, access logs, authentication records, application logs, cloud services, and more. By normalizing this data and analyzing it in real time, the Security Information and Event Management platform helps identify threats, detect patterns, and support incident response.
One of the key strengths of a Security Information and Event Management system is correlation. Instead of analyzing each log in isolation, the system looks for connections between events. For example, a login failure on one system, followed by a successful login on another, followed by an access to sensitive files—all from the same Internet Protocol address—may indicate credential compromise. On their own, each event looks benign. But together, they tell a story—and the Security Information and Event Management system is what connects the dots.
Security Information and Event Management tools also support alerting. Based on rules or behavior analytics, they can trigger alerts when certain thresholds are reached, patterns emerge, or anomalies occur. Alerts may be forwarded to analysts, integrated with ticketing systems, or used to trigger automated responses.
Let’s walk through a practical example. A manufacturing company uses a Security Information and Event Management system to collect logs from its firewall, domain controllers, and endpoint protection tools. One morning, the system detects a high volume of login attempts on multiple workstations, followed by unusual traffic leaving the network. The Security Information and Event Management platform correlates the events, generates a high-priority alert, and notifies the incident response team. The team isolates the affected systems, blocks the traffic, and begins remediation. Because the Security Information and Event Management system saw the bigger picture, the threat was caught and contained early.
Security Information and Event Management platforms also support compliance reporting. They can generate audit-ready documentation that shows who accessed what, when, and from where. They can demonstrate that monitoring is in place, that alerts are being reviewed, and that incidents are being handled. This makes Security Information and Event Management systems valuable not just for security—but for accountability and governance.
However, deploying a Security Information and Event Management platform requires planning. These systems can be resource-intensive, both in terms of infrastructure and personnel. You need to define data sources, configure parsing rules, manage storage, and tune alert thresholds. Without tuning, you may be overwhelmed by alerts. Without context, you may miss key signals. Security Information and Event Management platforms are powerful—but they need skilled operators and clear processes to deliver value.
To summarize, security monitoring tools come in many forms—and each plays a different role. Agent-based monitoring gives deep, endpoint-level visibility, while agentless monitoring provides broad, lightweight coverage. Both have strengths, and using them together creates a balanced monitoring strategy. Security Information and Event Management systems tie it all together—centralizing logs, correlating events, and enabling fast, informed responses to threats. These tools are the backbone of any effective security monitoring program.
For the Security Plus exam, expect to answer questions about the differences between agent-based and agentless monitoring, the benefits of Security Information and Event Management systems, and how these tools support incident detection and response. Be ready for scenarios involving monitoring design, alert analysis, or log correlation. Review terms like endpoint visibility, log normalization, correlation rule, event source, and alert fatigue—they’re all relevant and testable.
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