What data sources can SIEM security monitoring analyse?

SIEM security monitoring can analyse almost any machine-generated record that contains useful security context. The most valuable sources are those that show who performed an action, what happened, which system was involved, when it occurred and whether the action succeeded or failed. A SIEM brings these records into a common view so events from separate systems can be assessed together rather than in isolation.

Identity and authentication records show how accounts are being used. These may include successful and failed sign-ins, password changes, multi-factor authentication events, account lockouts, privilege changes and new account creation. They can help identify patterns such as repeated access failures, a privileged account being used unusually, or an account authenticating from locations and devices that do not fit its normal activity.

Endpoint and server telemetry provides detail about activity on individual computers and workloads. Useful records include process creation, script execution, software installation, service changes, local administrator activity, file access and device security events. This information can help connect an apparently harmless login with a suspicious process, an unauthorised configuration change or an attempt to establish persistence.

Network and perimeter data describes communications between devices, systems and external destinations. Firewalls, routers, wireless infrastructure, VPN services, proxies and network traffic sensors can provide connection attempts, blocked traffic, remote access activity, port use and data-transfer information. SIEM analysis can then compare network behaviour with identity and endpoint events to distinguish routine business traffic from activity that warrants investigation.

Application and database records are important because security incidents do not always appear at operating-system level. Applications may record changes to settings, unusual transactions, administrator actions, failed authorisation checks and access to sensitive functions. Database audit trails can show queries, changes to records, permission alterations and connections from unexpected accounts or systems.

Cloud and software-as-a-service audit data can include changes to virtual resources, storage permissions, access policies, service accounts, application registrations and administrative settings. These records are particularly useful for identifying configuration drift, excessive permissions and activity involving cloud identities that would not necessarily appear in traditional server logs.

Email and collaboration security data can add context to suspected phishing, account compromise and data loss. Depending on the systems in use, relevant events may include message filtering decisions, malicious attachment detections, forwarding-rule changes, mailbox access, unusual sign-in activity and sharing of documents with external users. The SIEM can correlate these events with endpoint and identity records to establish whether a message led to further activity.

Security control alerts provide another important source. Antivirus and endpoint detection tools, intrusion detection sensors, vulnerability scanners, web filters, data loss prevention systems and identity protection services may all generate alerts. Sending these alerts to a SIEM does not replace the original tool; it gives investigators a wider timeline and allows alerts to be assessed alongside supporting evidence from other systems.

Configuration, change and vulnerability information helps explain why an event may matter. Records of software versions, exposed services, policy changes, newly discovered weaknesses and changes to security controls can add risk context to an alert. For example, an attempted connection is more significant when it targets a newly exposed service or a system with a relevant unresolved vulnerability.

A SIEM can also ingest contextual data rather than activity logs alone. Examples include asset inventories, user and role directories, network address information, threat intelligence indicators and lists of approved administrators or trusted services. This context helps the SIEM judge whether an event involves a critical asset, a privileged user or an address associated with known malicious activity.

The practical value of each source depends on the quality of its records and how they are connected. Events should normally include a reliable timestamp, source system, account or device identifier, action, result and relevant network information. The SIEM may need to parse different formats, normalise field names, account for time zones and remove duplicate records before correlation rules can use the data consistently.

Not every available log needs to be collected. Organisations usually prioritise sources according to business risk, regulatory requirements, the sensitivity of the systems involved and the questions they need monitoring to answer. Collecting large volumes of low-value data can increase storage and investigation overhead without improving detection. Missing or incomplete sources can also create blind spots, so coverage should be reviewed when systems, applications, suppliers or working practices change.

For a small or medium-sized organisation, a sensible starting point may be identity activity, endpoint security events, perimeter controls, key cloud services, business-critical applications and backup or administrative systems. S2 Technology Group can help organisations assess which sources are relevant to their environment and integrate SIEM monitoring with wider cyber security arrangements, without treating every log as equally important.