Every security incident leaves a trail — in firewall logs, email records, sign-in events and endpoint telemetry. The problem for most Australian businesses is that nobody is watching that trail. A SIEM brings all of those logs into one place, watches them continuously, and turns thousands of daily events into the handful of alerts that actually matter. This guide explains what SIEM is, what it does, whether your business needs one, and how managed SIEM and SOC services fit into a Microsoft 365 environment.
What is SIEM?
SIEM stands for Security Information and Event Management. A SIEM platform collects log data from across your IT environment — servers, endpoints, network devices, cloud services, and applications — aggregates it in a central location, analyses it in real time for signs of threat activity, and generates alerts when suspicious patterns are detected. The purpose of a SIEM is to give security teams visibility across an entire environment that would be impossible to achieve by reviewing individual system logs.
What does SIEM do?
A SIEM platform performs five core functions:
- Log collection and centralisation — ingests logs from Windows endpoints, Azure AD/Entra, Microsoft 365, firewalls, servers, and applications.
- Correlation — applies rules and machine learning to connect events across systems that individually look benign but together suggest an attack.
- Alerting — generates prioritised alerts when a correlation rule fires.
- Forensics — provides a searchable log history for investigating incidents after the fact.
- Reporting — generates compliance reports showing log retention, security events, and response activities.
SIEM vs SOC — what's the difference?
A SIEM is a technology — software that collects, analyses, and alerts on log data. A SOC (Security Operations Centre) is a function — people who monitor those alerts, triage them, investigate threats, and respond to incidents. You can have a SIEM without a SOC (automated alerting with no human review), but the alerts generated will largely go unresponded to. For Australian businesses without an in-house security team, a managed SOC via a platform like Huntress is more practical — it combines SIEM-like detection with human-reviewed triage and incident response.
Do Australian businesses need a SIEM?
Organisations that should consider SIEM: businesses with 100+ users where manual log review is impractical, organisations handling sensitive data with regulatory log retention requirements (APRA CPS 234, DISP, Privacy Act), businesses required to demonstrate 12-month log retention for cyber insurance or government panels, and organisations at Essential Eight Maturity Level 2 (which requires centralised logging). Businesses under 50 users typically start with managed EDR and SOC before investing in a full SIEM deployment.
Microsoft Sentinel — SIEM for Australian Microsoft 365 businesses
Microsoft Sentinel is Microsoft's cloud-native SIEM platform, built on Azure. For Australian businesses already on Microsoft 365 and Azure, Sentinel integrates natively — it ingests Microsoft 365 audit logs, Entra sign-in events, Defender alerts, and Azure activity logs without additional connectors. Pricing is based on data ingestion volume. Mycelium 365 deploys and manages Microsoft Sentinel for clients where a SIEM is required — typically alongside Huntress managed SOC for human-reviewed alert triage.
How Mycelium 365 delivers managed security monitoring
Mycelium 365 delivers 24/7 managed SOC via Huntress — covering endpoint, identity, and email threat detection with human-reviewed alert triage. For clients requiring a full SIEM deployment, we deploy Microsoft Sentinel connected to their Microsoft 365 and Azure environment. The combination of Sentinel (SIEM) and Huntress (managed SOC) provides enterprise-grade security visibility for Australian SMBs at a predictable monthly cost. Contact us to discuss your security monitoring requirements.