SIEM

What it means

SIEM, security information and event management, is a system that collects records, or logs, from many sources: servers, workstations, firewalls, applications, cloud services, sign-in systems and antivirus tools. It stores the data in one place, normalises the format and makes it searchable.

Its key function is correlation, finding links between events from different sources. Individual events may look harmless but together form a suspicious pattern, such as several failed logins, then a successful login from another country and a large data download. SIEM raises an alert on such a situation.

SIEM is the technical foundation of security monitoring. The system alone is not enough, though; someone has to assess alerts and respond. The team that does this is called a SOC. SIEM also serves as an archive of audit logs for investigating incidents and demonstrating regulatory compliance.

How it works in practice

For companies covered by NIS2 and the Slovak cybersecurity act, logging and analysing security events is one of the required areas. A SIEM, or a service providing one, helps meet the requirements for detection, reporting incidents within short deadlines and retaining records.

Small and medium-sized companies usually cannot afford their own SIEM and a round-the-clock team. The answer is a managed detection service from an external provider running SIEM and SOC for several clients. The company pays a monthly fee and receives alerts only on genuinely significant events, with advice on what to do.

In deployment it matters to choose the right sources. Start with the most sensitive systems: sign-in and identity management, email, EDR on endpoints, the firewall and key applications. Detection rules need tuning so the system does not produce thousands of false alarms that nobody can check.

What to watch out for

The most common mistake is a SIEM that collects logs but nobody watches. Such a system gives a false sense of security and is useful only after an incident, during the investigation. Before buying, be clear who will assess alerts, how quickly and under what incident response procedure.

Watch costs and data protection. SIEM pricing often depends on data volume, which can grow fast. Logs also contain personal data of staff and customers, so retention periods and access rights must be set and employees informed about monitoring in line with the GDPR.