SIEM: Understanding Its Role in Threat Detection

A SIEM (Security Information and Event Management) is a security platform that collects, aggregates, and analyzes in real time the logs and events generated across an organization’s entire information systems: servers, firewalls, applications, endpoints, and cloud services. Its goal is to detect threats, correlate suspicious events, and facilitate incident response.

How does it work?

A SIEM operates in four main stages. The first stage is collection: the SIEM ingests logs from all infrastructure sources, from firewalls and servers to security solutions (EDR, antivirus, proxy). The volume can reach tens of billions of events per day in large organizations.

The second stage is normalization: logs from heterogeneous sources are converted into a unified format to enable correlation. The same event may be described differently by a Palo Alto firewall and a Windows server, and the SIEM harmonizes this data.

The third stage is correlation: the SIEM applies detection rules to identify suspicious behaviors. For example, a login from an unusual country followed by a massive data download can trigger an alert. Modern SIEMs also incorporate machine learning to detect behavioral anomalies.

The fourth stage is alerting and response: when a threat is detected, the SIEM generates an alert with the context needed for the security team to investigate and respond. The most advanced platforms integrate with SOAR tools to automate certain response actions.

The most widely used SIEM solutions include Splunk, Microsoft Sentinel, IBM QRadar, Elastic Security, and Google Chronicle.

Why does it matter?

The SIEM is the central pillar of threat detection in modern organizations. Without it, security teams are blind to the volume of events generated by infrastructure, unable to correlate the weak signals that reveal an ongoing attack.

For businesses subject to regulations (GDPR, NIS2, SOC 2, ISO 27001), the SIEM provides the traceability and evidence needed to demonstrate compliance. It also helps reduce mean time to detect (MTTD) and mean time to respond (MTTR) to incidents.

However, a SIEM has a major blind spot: it can only analyze events internal to the organization. It cannot see what happens externally, particularly your employees’ credentials circulating on the dark web after being stolen by an infostealer.

How Stealed protects you

Stealed fills the SIEM’s blind spot by providing visibility into external threats. Where the SIEM monitors your internal infrastructure, Stealed monitors the dark web, Telegram channels, and cybercriminal forums to detect your employees’ credentials compromised by infostealers.

Stealed alerts can feed directly into your SIEM via webhooks or API, enriching your correlation rules with external indicators of compromise. For example, a Stealed alert indicating that a VPN credential has leaked can be correlated with your SIEM’s VPN connection logs to verify whether the credential has already been exploited.

Learn more: read our Cyber Threat Intelligence guide to understand how to integrate external intelligence feeds into your security strategy.

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