What Is a SIEM?

Reviewed by Grant McDonald · February 24, 2025

Security Information and Event Management (SIEM) is software that improves security awareness of an IT environment by combining security information management (SIM) and security event management (SEM). SIEM solutions enhance threat detection, compliance, and security incident management through the gathering and analysis of real-time and historical security event data and sources.

How a SIEM works

A SIEM collects and combines data from event sources across an organization’s IT and security framework. This includes host systems, networks, firewalls, and antivirus security devices. The software allows security operations teams to gain attacker insights with threat rules derived from insight into attacker tactics, techniques and procedures (TTPs) and known indicators of compromise (IOC)s.

The threat detection element itself can help to detect threats in emails, cloud resources, applications, networks, external threat intelligence sources, and endpoints. When an incident or event is identified, analyzed, and categorized, the SIEM works to deliver reports and notifications to the appropriate stakeholders within the organization. 

This can include user and entity behavior analytics (UEBA), which analyzes behaviors and activities to monitor for abnormal behaviors that could indicate a threat. It can also detect lateral movement and compromised accounts.

This is similar to the security analytics component that detects anomalies in data to inform threat hunting for previously unseen threats.

Four benefits of a SIEM

Benefit #1: Enhanced Threat Hunting and Detection

By aggregating and correlating data from multiple sources, a SIEM helps uncover stealth attackers and multistage attack patterns that individual security tools might miss. This includes detecting advanced persistent threats (APTs), insider threats, and ransomware.

Benefit #2: Improved Efficiency and Response Time

A SIEM can harness the power of global threat intelligence to enable rapid discovery of events involving communications with suspicious or malicious IP addresses. Attack paths and past interactions can be quickly identified, reducing response time for more rapid disposition of threats to the environment.

Benefit #3: Expanded Visibility

A SIEM brings data and insights from across enterprise environments (including on-premises, cloud, multicloud, and hybrid—though not collaboration or air-gapped). When used in conjunction with endpoint detection and response (EDR) and network detection and response (NDR), they provide a unified view of security events.

Benefit #4: Compliance Management

SIEMs automate the gathering, storage, and reporting of security event data. This is necessary to meet various regulatory requirements and standards like HIPAA, PCI DSS, GDPR, and SOX.

SIEM best practices

• Set Your Scope. Determine the scope of your SIEM implementation. Build policy-based rules defining activities and logs your SIEM should monitor. Use that policy and compare its rules to external compliance requirements to determine what type of dashboard and reporting your organization requires.
• Fine-tune Correlation Rules. A SIEM presents its own set of preconfigured correlation rules. Your security team can fine-tune the software to your organization’s needs by enabling everything by default, observing the behavior, and identifying tuning opportunities to increase detection efficacy and reduce false positives.
• Identify Compliance Requirements. Meeting compliance requirements is an important benefit to most organizations using a SIEM. An organization should analyze a software’s ability to support specific compliance mandates as required to meet organizational auditing requirements.
• Monitor Access to Critical Resources. A SIEM should monitor various aspects of critical resources including privileged and administrative address, unusual user behavior on systems, remote login attempts, and system failure.
• Defend Network Boundaries. All vulnerable areas on a network should be monitored by a SIEM, EDR, and NDR, including firewalls, routers, ports, and wireless access points.
• Test Your SIEM. Important alert metrics and the need for SIEM reconfiguration can be produced when conducting test runs of your SIEM implementation and assessing how it reacts.
• Implement a Response Plan. Security incidents can only be dealt with in a timely manner using an incident response plan. Organizations should plan how it will alert staff following a SIEM alert.

Why organizations need a next-gen SIEM

SIEM software has been around since 2005 but has evolved significantly since its genesis. As technology advances, attacks evolve and SIEM solutions have had to evolve with them. A next-gen SIEM—an approach that began to emerge in 2017—offers significant improvements over traditional systems, primarily by leveraging AI and cloud-native infrastructure for superior scalability and faster search performance. Traditional SIEMs, which often rely on on-premises infrastructure, experience performance degradation as they scale.

A major difference lies in alert management. Traditional, rules-based SIEMs frequently generate numerous individual alerts, leading to “alert fatigue” and slowing an analyst's ability to contextualize threats. In contrast, next-gen SIEMs use AI-powered analytics to correlate multiple events into fewer, more actionable alerts.

This consolidated view of telemetry helps analysts prioritize threat events by severity. It reduces the time spent sifting through alerts and false positives, allowing security teams to focus on critical incidents and helping to ensure that subtle, low-level signals that could indicate an attack are not overlooked.

Key Next-gen SIEM Attributes

Next-gen SIEMs provide a number of key attributes to address today’s cybersecurity needs:

• They are increasingly powered by AI and machine learning to enhance analytical capabilities, automatically establish behavioral baselines, identify complex or unknown threats, and reduce false positives.
• They integrate or include security orchestration, automation, and response (SOAR) capabilities. While SIEM focuses on detection and analysis, SOAR involves automating workflows and executing predefined playbooks to respond to incidents, speeding up mitigation.
• Their open architecture allows quicker integration with enterprise infrastructure including cloud, on-premises, and BYOD, which is also scalable.
• They can integrate threat intelligence from custom, open source, and commercial sources.
• Real-time visualization tools understand the most important, high-risk activities to prioritize alerts. This includes the ability to measure status against regulatory frameworks (such as PCI DSS) for risk prioritization and management.
• UEBA can understand event context and recognize intent within specific scenarios. By using UEBA, the software is able to highlight significant changes in behavior.
• They can be customized, though this often requires coding expertise, especially in areas such as SOAR, which can slow execution. Trellix no-code hyperautomation provides a faster, more streamlined alternative.

The SOC triad: Orchestrating SIEM, EDR, and NDR synergy

The synergy between SIEM, EDR, and NDR solutions creates a comprehensive defense strategy often referred to as the "SOC triad." While each technology has specific strengths, their integration eliminates blind spots and allows for more accurate threat detection and faster response.

How They Work Together

To understand their synergy, it helps to first identify what those blind spots are when each tool is used in isolation:

• SIEM (The Central Hub). A SIEM acts as the system of record and the centralized command center. It provides breadth by aggregating logs from the entire IT estate (firewalls, identity systems, cloud, etc.) for compliance and high-level correlation. However, a SIEM is dependent on the quality of logs it receives; if a device doesn't generate a log, the SIEM may not see it.
• EDR (The Device Specialist). EDR provides depth at the device level. It monitors processes, file changes, and command executions on servers and workstations. However, EDR cannot monitor devices where agents cannot be installed, such as IoT devices, printers, or legacy operational technology (OT).
• NDR (The Network Watcher). NDR provides depth at the network level. It monitors traffic to detect lateral movement, command-and-control (C2) activity, and anomalies. It fills the gap left by EDR by monitoring unmanaged devices (IoT/OT), but it cannot see what happens "inside" a device (like a file change).

When integrated, these tools compensate for each other's weaknesses to create a unified security posture. A SIEM provides the bird's-eye view of the entire estate, managing security operations across silos. EDR and NDR provide deep, high-fidelity insights into specific assets.

While EDR and NDR improve the accuracy of detections on endpoints and networks, they don't always have the capacity for long-term storage or compliance reporting. A SIEM ingests alerts from these tools to provide the necessary historical retention and compliance frameworks.

Correlating Disparate Events

The most critical synergy is the ability to correlate events that look harmless in isolation but indicate an attack when combined.

• Lateral Movement. An attacker moving through the network might use valid credentials (bypassing identity alerts) and standard tools (bypassing EDR malware checks). However, NDR can detect the unusual traffic pattern of one computer connecting to many others. By feeding this telemetry into the SIEM, it can be correlated with a user login event to identify a compromised insider.
• Advanced Persistent Threats (APTs). EDR might detect a suspicious process on a laptop. Simultaneously, NDR might detect that laptop communicating with a known malicious IP address. The SIEM correlates these two separate alerts into a single, high-priority incident, confirming that the malware is active and communicating externally.

Eliminating Blind Spots

Using these tools together expands visibility:

• Unmanaged Devices. Because NDR monitors the network traffic rather than the device itself, it covers IoT, OT, and cloud assets that EDR cannot.
• Evasion Techniques. If an attacker disables logging on a compromised server (blinding the SIEM) or kills the EDR agent, the NDR will still capture the network traffic generated by the attack, ensuring the activity is still detected.

Providing a Unified Response

The synergy extends to response. Next-gen SIEMs include SOAR capabilities that leverage EDR and NDR to execute actions.

• Automated Containment. When the SIEM detects a high-confidence threat based on correlated data, it can instruct the EDR to isolate the infected laptop and instruct the firewall (via network integration) to block the malicious IP address.
• Investigation. A SIEM can query the EDR for a snapshot of active processes or the NDR for packet captures, pulling this forensic data into a single dashboard for the analyst.

Summary of Interplay

SIEM FAQ