What Is SIEM? A Guide to Security Information and Event Management
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Key takeaways
The growing number of cyber threats and the complexity of information systems are pushing businesses to improve how they detect suspicious activity on their networks. When security data comes from many different sources, manual monitoring can quickly become unmanageable.
Businesses can benefit greatly from a SIEM to address these challenges. This technology centralises and analyses security information, helping teams identify the events that need their attention, which makes it an essential part of any cybersecurity strategy.
SIEM stands for Security Information and Event Management. It is a solution that collects and centralises the logs and events generated by the different components of a company's information system, in order to analyse them and identify potentially suspicious activity.
This data can come from many sources. A SIEM brings all of this information together in a single environment, giving security teams an essential overview of what is happening.
A cyber attack often leaves traces in the information system, such as a change in privileges following an unusual login attempt. Taken separately, each of these events can look harmless. Viewed together, they can reveal malicious activity.
This is where SIEM security monitoring proves its value. By centralising and correlating events from different sources, it identifies unusual behaviour and alerts security teams. It also supports cybersecurity incident response by allowing analysts to go back through recorded events to understand what happened, which systems were affected and which actions were taken.
A SIEM does not replace other protective measures, but it improves an organisation's ability to detect and analyse threats.
A SIEM works through several stages, from data collection to incident response. Each stage builds on the one before it.
The first step is to retrieve the data produced by the different components of the information system. A SIEM can collect logs from operating systems, servers, applications and many other sources. This information is then grouped together on a centralised platform.
Collecting the data is not enough. The next step is being able to link it together. To do this, the SIEM normalises the information coming from different sources, then looks for connections between events. Correlation rules can, for example, link several failed authentication attempts to a successful login from an unusual location, followed by access to a sensitive resource.
Modern SIEM solutions can also include behavioural analysis or machine learning functions to identify deviations from normal patterns of behaviour.
When a rule is triggered or unusual activity is detected, the SIEM generates an alert. Alerts can be classified and prioritised based on criteria such as the nature of the event, the sensitivity of the system involved or the estimated level of risk. Analysts can then focus their attention on the most concerning events.
Once an alert has been identified, security teams can use the information centralised in the SIEM to carry out their investigation. This information can help reconstruct the timeline of events, identify the accounts or devices involved and determine the scope of the incident. This guides the response to the cybersecurity incident and helps teams take the appropriate measures.
Although the features of SIEM tools vary from one solution to another, most SIEM platforms are built on the following elements. Each one plays a distinct role in monitoring and protecting the information system.
Log management is the foundation of a SIEM. The platform centralises logs from multiple sources to make them easier to store, search and analyse. This centralisation also preserves a history of events, which is useful both for investigations and as part of a wider data security strategy.
A SIEM provides continuous monitoring of the events reported by connected systems. Teams can track logins, configuration changes, network events and any other activity relevant to security.
The platform analyses the collected data to identify events, or combinations of events, that could signal a threat.
When a behaviour matches the defined criteria, the SIEM can create an alert for analysts. The associated information allows them to examine the context of the event, look for related activity and determine whether it is a false positive or a genuine incident.
Centralising logs also makes it easier to produce reports. The company can use the available data to document its activities, keep records of events or demonstrate that monitoring measures are in place.
The benefits of SIEM solutions come from bringing security information together on a single platform. This delivers several advantages for security teams and the wider organisation.
One of the main advantages is reducing the fragmentation of information. Teams no longer need to check the logs of each application, server or device individually. They have a centralised view that makes it easier to track events across the entire information system.
Automatic correlation brings out behaviours that would be difficult to spot through manual analysis. Detection becomes faster, giving teams more time to analyse and contain a threat before it spreads or causes significant damage.
When an incident occurs, analysts need to understand exactly how it unfolded. Retaining and centralising events helps teams find the traces left by the attacker and build a timeline to identify the point of entry, the systems affected and the actions carried out.
A SIEM also gives a more complete picture of the IT environment. This visibility can highlight misconfigured devices, unusual behaviour or areas that are not sufficiently monitored. The insights gathered can then feed into cybersecurity governance and help decision-makers make better-informed choices.
Many regulations, standards and frameworks require organisations to have logging, monitoring or audit-trail mechanisms in place. A SIEM centralises the information and automates certain reports, reducing the work needed to retrieve the evidence requested during an audit.
Installing a SIEM solution is not enough to improve security on its own. Its effectiveness depends largely on the quality of its configuration and how well it is integrated into the company's processes.
Before choosing or configuring a solution, the organisation needs to determine what it wants to monitor. Which assets are the most sensitive? Which threats should be detected as a priority? Which events should trigger an alert? This analysis defines precise use cases.
Not all data has the same value from a security perspective. The organisation needs to identify the sources most likely to provide useful information (identity systems, critical applications, firewalls, endpoints, servers, cloud infrastructure, network equipment or detection solutions) to achieve sufficient coverage without collecting data unnecessarily.
Rules that are too broad can generate a large number of false positives and lead to alert fatigue. Rules that are too restrictive risk letting some malicious activity through. Thresholds, detection scenarios and priority levels must be adapted to the company's context and adjusted based on the incidents observed.
The company must determine who receives alerts, how they are analysed, when they should be escalated and what measures should be taken once an incident is confirmed. These processes should set out clear roles and responsibilities so that nobody hesitates when a threat arises.
Information systems evolve constantly, and so do threats. The SIEM's configuration must therefore evolve with them. Regularly review the relevance of rules, the quality of collected logs, false positives, missing data sources and the effectiveness of alerts to keep the setup aligned with the organisation's risks. DPO Consulting can support you with these tasks.
SIEM is sometimes confused with other cybersecurity concepts and tools. However, SOC, SOAR, XDR and log management solutions each serve different functions. Understanding the differences clarifies where SIEM tools fit within a security architecture.
A SOC (Security Operations Centre) is a function or team responsible for monitoring, detecting, analysing and handling security incidents. A SIEM is one of the technologies this team can use. In an organisation running a SOC, analysts rely on the SIEM platform to centralise events, receive alerts and carry out their investigations.
SOAR (Security Orchestration, Automation and Response) focuses primarily on orchestrating and automating security operations. Where a SIEM collects and analyses events to detect threats, SOAR chains certain actions together automatically based on a predefined playbook. The two technologies are often complementary.
XDR (Extended Detection and Response) gathers and analyses information from several security layers, including endpoints, networks, identities, email and cloud environments. A SIEM takes a broader approach by centralising logs from many sources across the information system. XDR is more focused on integrated detection and response based on security telemetry data.
A log management solution is designed above all to collect, store, search and retain logs. A SIEM goes further by giving this data a purpose that is specifically focused on security. A log management platform can therefore be a useful building block in the security infrastructure without offering the full range of functions found in SIEM tools.
Implementing a SIEM must respond to the risks, systems and obligations specific to each organisation. The starting point is identifying critical assets, the threats to monitor, the relevant data sources and the processes to trigger when an alert appears. The SIEM must then fit into an overall strategy that combines governance, prevention, detection and incident response.
DPO Consulting supports organisations in assessing their risks and putting in place measures suited to their cybersecurity and compliance challenges. This support helps integrate the SIEM into a coherent approach to data protection and incident management. Explore our cybersecurity compliance services to see how this fits with your obligations.
Request a quote online to find out more.
A security information and event management (SIEM) platform is used to collect and centralise events and logs from across the information system so they can be analysed. It helps detect suspicious activity, generate alerts, support investigations and produce security or compliance reports.
A SIEM system includes mechanisms for collecting and centralising data, storage and normalisation capabilities, an analysis and correlation engine, an alerting system, and search, visualisation and reporting tools.
Not always. It depends on the level of risk, the complexity of the information system, the resources available and the company's regulatory obligations. A small organisation with a simple IT environment may prefer lighter monitoring solutions, while an SME handling sensitive data or running a complex infrastructure may benefit from a SIEM.
A SIEM analyses events collected from different sources to look for suspicious activity. To do this, it uses correlation rules, thresholds, indicators of compromise and, depending on the solution, behavioural analysis or machine learning. When a risk scenario is identified, an alert is sent to the security team.
A SIEM can collect logs and events from many sources, including servers, workstations, firewalls, routers, applications, databases, identity systems, cloud services and cybersecurity tools.
The retention period for SIEM logs depends on the applicable legal and regulatory obligations, investigation needs, the nature of the data recorded, the risks involved and the company's storage constraints. Each organisation therefore needs to define a retention policy that is justified by its needs.
The cost of a SIEM solution depends on the solution selected and the environment to be monitored. Beyond the licence or service fee, you also need to account for the resources required for configuration, maintenance and alert analysis.
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