Security information and event management (SIEM) is an approach to security management that seeks to provide a holistic view of an organization's information technology (IT) security. The acronym is pronounced "sim" with a silent "e."
The underlying principle of a SIEM system is that relevant data about an enterprise's security is produced in multiple locations and being able to look at all the data from a single point of view makes it easier to spot trends and see patterns that are out of the ordinary.
SIEM combines SIM (security information management) and SEM (security event management) functions into one security management system. A SEM system centralizes the storage and interpretation of logs and allows near real-time analysis which enables security personnel to take defensive actions more quickly. A SIM system collects data into a central repository for trend analysis and provides automated reporting.
By bringing these two functions together, SIEM systems provide quicker identification, analysis and recovery of security events. They also allow compliance managers to confirm they are fulfilling an organization's legal compliance requirements. SIEM systems collect logs and other security-related documentation for analysis. Most SIEM systems work by deploying multiple collection agents in a hierarchical manner to gather security-related events from end-user devices, servers, network equipment -- and even specialized security equipment like firewalls, antivirus or intrusion prevention systems. The collectors forward events to a centralized management console, which performs inspections and flags anomalies. To allow the system to identify anomalous events, it’s important that the SIEM administrator first creates a profile of the system under normal event conditions.
At the most basic level, a SIEM system can be rules-based or employ a statistical correlation engine to establish relationships between event log entries. In some systems, pre-processing may happen at edge collectors, with only certain events being passed through to a centralized management node. In this way, the volume of information being communicated and stored can be reduced. The danger of this approach, however, is that relevant events may be filtered out too soon.
SIEM systems are typically expensive to deploy and complex to operate and manage. While Payment Card Industry Data Security Standard (PCI DSS) compliance has traditionally driven SIEM adoption in large enterprises, concerns over advanced persistent threats (APTs) have led smaller organizations to look at the benefits a SIEM managed security service provider (MSSP) can offer.