What Is SIEM and Does My Business Need It?

Quick answer: SIEM (Security Information and Event Management) collects logs from all your systems, correlates events, detects threats, and provides investigation capability. It's essential for compliance-heavy environments and larger organisations. For smaller businesses, managed security services often provide SIEM benefits without the complexity.

What SIEM Does

Log collection

Gathers logs from everywhere:

• Servers and workstations
• Firewalls and network devices
• Cloud services (Microsoft 365, Azure, AWS)
• Applications
• Security tools

One place to see everything. No more checking five different consoles.

Event correlation

Connects dots across systems:

• Failed login on server A + successful login on server B + data exfiltration = attack chain
• Individual events look normal; pattern reveals the threat

Sees attacks that individual tools miss.

Threat detection

Rules and analytics to identify:

• Known attack patterns
• Anomalous behaviour
• Policy violations
• Indicators of compromise

Alerts when something's wrong rather than waiting for obvious damage.

Investigation

When incidents happen:

• Search across all log data
• Reconstruct what happened
• Identify scope and impact
• Gather evidence

Forensic capability built in.

Compliance

Many regulations require:

• Centralised logging
• Log retention (often 12+ months)
• Audit trails
• Monitoring evidence

SIEM provides the evidence.

Who Needs SIEM

You probably need SIEM if:

Compliance requires it:

• ISO 27001 expects centralised logging
• NIS2 requires security monitoring
• Defence contracts often mandate it
• Cyber insurance may expect it

You have complex environments:

• Multiple locations
• Many systems to monitor
• Hybrid cloud
• Third-party integrations

You need forensic capability:

• Regulated industry
• Handle sensitive data
• Need to investigate incidents thoroughly

You're a valuable target:

• Defence supply chain
• Critical infrastructure
• Financial services
• Healthcare

You might not need full SIEM if:

You're a small, simple environment:

• Under 50 users
• Straightforward Microsoft 365 setup
• No compliance mandates
• Basic security monitoring is sufficient

In this case: MDR and cloud-native monitoring may be enough.

SIEM Options

Traditional SIEM (Splunk, QRadar, etc.)

• Powerful and flexible
• Expensive (licensing, storage, expertise)
• Complex to deploy and manage
• Requires dedicated staff

Best for: Large enterprises with security teams

Cloud-native SIEM (Microsoft Sentinel, etc.)

• Pay-as-you-go pricing
• Integrates well with cloud environments
• Still requires expertise to configure
• Can scale up or down

Best for: Mid-size organisations in cloud environments

Managed SIEM

• Provider manages the platform
• You get alerts and reporting
• Lower expertise requirement
• Predictable pricing

Best for: Organisations without dedicated security staff

SIEM Costs

Traditional SIEM:

• Licensing: £20,000-100,000+/year
• Infrastructure: Significant
• Staff: 1-2 FTE minimum
• Total: £100,000+/year for mid-size deployment

Cloud SIEM:

• Consumption-based (per GB ingested)
• Microsoft Sentinel: Roughly £2-5 per user/month for typical SME
• Still needs configuration expertise

Managed SIEM:

• Fixed monthly fee
• £5-15 per user/month typical
• Includes management and monitoring

SIEM vs MDR

People often confuse these:

They complement each other. MDR detects endpoint threats. SIEM provides broad visibility and forensics.

Our SIEM Approach

We partner with Assuria—UK-based SIEM:

• UK data centres (important for defence, regulated sectors)
• Managed service (we run it)
• Compliance-focused reporting
• UK-owned technology

For managed clients:

• SIEM integrated with other security tools
• Alerts triaged by our team
• Compliance reporting included
• 12+ month log retention

You get SIEM benefits without SIEM complexity.

---

about managed SIEM.

---