How to Implement Azure Sentinel for Security Monitoring

As cyber threats facing UK businesses continue to grow in both volume and sophistication, the need for comprehensive security monitoring has never been greater. Traditional approaches — relying on firewalls, antivirus, and occasional log reviews — are no longer sufficient to detect modern threats that use stealth, persistence, and lateral movement to compromise organisations. What businesses need is a Security Information and Event Management (SIEM) solution that aggregates security data from across their entire environment, applies intelligent analytics to detect threats, and enables rapid investigation and response.

Microsoft Sentinel (formerly Azure Sentinel) is Microsoft's cloud-native SIEM and Security Orchestration, Automation, and Response (SOAR) platform, built on top of Azure. It provides intelligent security analytics across your entire organisation, collecting data from users, devices, applications, and infrastructure — both on-premises and in the cloud. For UK businesses already invested in the Microsoft ecosystem through Microsoft 365 and Azure, Sentinel provides a natural and powerful extension of their security capabilities.

This guide explains what Azure Sentinel is, how it works, and provides a practical implementation roadmap for UK businesses looking to implement enterprise-grade security monitoring without the complexity and cost traditionally associated with SIEM platforms.

What Is Azure Sentinel?

Azure Sentinel is a cloud-native SIEM and SOAR solution that uses artificial intelligence and machine learning to detect, investigate, and respond to security threats across your organisation. Unlike traditional SIEM products that require significant on-premise hardware, complex deployment, and dedicated security analysts to operate, Sentinel is delivered as a service from Azure, with no infrastructure to manage and built-in AI that reduces the expertise required to gain value from the platform.

At its core, Sentinel performs four functions. It collects security data from across your environment using data connectors — pulling in logs from Microsoft 365, Azure Active Directory, firewalls, servers, endpoints, and third-party security tools. It detects threats using a combination of built-in analytics rules, machine learning models, and threat intelligence feeds. It investigates alerts using interactive investigation graphs that show the relationships between entities (users, IP addresses, devices) involved in a potential incident. And it responds to confirmed threats using automated playbooks that can isolate compromised accounts, block malicious IP addresses, or notify your security team — all without manual intervention.

Implementation Roadmap

Implementing Azure Sentinel follows a structured approach that can be completed in phases, allowing you to gain value quickly while expanding coverage over time. The following roadmap is designed for UK SMEs and mid-market businesses with an existing Microsoft 365 and Azure footprint.

Phase 1: Foundation (Weeks 1-2)

Create a Log Analytics workspace in an Azure UK region (UK South or UK West) to ensure data residency within the United Kingdom. This workspace is where all your security data will be stored and analysed. Enable Azure Sentinel on this workspace — this is a single-click operation in the Azure portal that activates all Sentinel features.

Connect your most valuable data sources first. For most UK businesses, this means Microsoft 365 (which captures email, SharePoint, OneDrive, and Teams activity), Azure Active Directory (which captures sign-in and audit logs), and Microsoft Defender for Endpoint (which captures endpoint security events). These connectors are built into Sentinel and can be enabled in minutes with no additional configuration.

Phase 2: Detection (Weeks 3-4)

Enable Sentinel's built-in analytics rules, which provide immediate detection capability for common threats. Microsoft provides hundreds of pre-built rules covering scenarios such as impossible travel (a user signing in from London and then from Moscow within an hour), brute force attacks, suspicious email forwarding rules, and known malicious IP addresses. Review and enable the rules relevant to your environment.

Configure the built-in User and Entity Behaviour Analytics (UEBA) module, which uses machine learning to establish a baseline of normal behaviour for each user and entity in your organisation. Once the baseline is established (typically after two to four weeks of data collection), UEBA will detect anomalous behaviour — such as a user accessing systems they have never accessed before, or logging in at unusual hours — that may indicate a compromised account.

Phase 3: Investigation and Response (Weeks 5-8)

Once data is flowing and detections are generating alerts, configure the investigation and response capabilities. Sentinel's investigation graph provides a visual tool for exploring the relationships between alerts, users, IP addresses, and devices involved in a potential incident. When an alert fires — for example, "suspicious sign-in from unusual location" — the investigation graph shows you which user was involved, what other activities that user performed around the same time, which IP address was used, and whether that IP has been associated with other alerts.

Create automated playbooks using Azure Logic Apps to respond to common alert types without manual intervention. For example, when a high-severity alert is generated for a compromised account, a playbook can automatically disable the account, revoke active sessions, reset the password, and send a notification to your IT security team — all within seconds of the alert being raised. This automated response dramatically reduces the time between detection and containment.

Cost Management for Azure Sentinel

Azure Sentinel pricing is based on the volume of data ingested into your Log Analytics workspace. As of 2025, the pay-as-you-go rate is approximately £2.10 per GB per day, with commitment tiers offering discounts of up to 50 per cent for higher volumes. For most UK SMEs, the daily data volume from Microsoft 365, Azure AD, and endpoint security sources ranges from 2 to 15 GB per day.

To manage costs effectively, focus your data collection on high-value security logs rather than attempting to ingest everything. Microsoft 365 and Azure AD logs, which provide the most security value per GB, are typically the most cost-effective data sources. Windows security event logs can be filtered to collect only security-relevant events rather than all events, reducing volume significantly. Firewall logs can be sampled or filtered to capture only denied connections and anomalous traffic rather than every permitted connection.

Microsoft also offers a benefit for Microsoft 365 E5 customers: up to 5 GB per day of free data ingestion for specific Microsoft data sources. For businesses already on E5 licences, this can significantly reduce Sentinel costs, as Microsoft 365 and Azure AD logs often account for the majority of ingested data.

UK Compliance Benefits of Azure Sentinel

For UK businesses subject to regulatory requirements, Azure Sentinel provides significant compliance benefits. The platform's audit logging, threat detection, and incident response capabilities directly support compliance with UK GDPR Article 32 (security of processing), which requires organisations to implement "appropriate technical and organisational measures" including "a process for regularly testing, assessing and evaluating the effectiveness of technical and organisational measures for ensuring the security of the processing."

Sentinel's data residency options ensure that all security data remains in UK Azure regions, satisfying data sovereignty requirements. The platform's retention policies allow you to define how long security data is retained, supporting compliance with both minimum retention requirements (where regulations require you to keep logs for a specific period) and maximum retention requirements (where GDPR's data minimisation principle requires you to delete data when it is no longer needed).

For businesses pursuing Cyber Essentials Plus certification, the NCSC recommends implementing security monitoring to detect and respond to cyber incidents. Azure Sentinel provides exactly this capability, and its implementation demonstrates to assessors that your organisation takes threat detection seriously.