Microsoft 365 Security Audit Service

Most tenants are configured for productivity, not defence. Default settings leave gaps that attackers know how to use, and those gaps rarely show up until something goes wrong. The audit turns "we think we're secure" into a ranked list of exactly what is wrong and what to do about it. AMVIA's part of the Microsoft 365 security practice — UK engineers who configure these tenants every day.

What does an M365 security audit cover?

An M365 security audit reviews every control that decides who gets into your tenant and what they can do once inside. We assess identity, data, devices and apps against Microsoft's own benchmarks, then score the risk of each gap so you fix the dangerous ones first.

The audit examines:

• Identity — MFA enforcement, Conditional Access policies, legacy authentication, and admin role assignments.
• Data — external sharing settings, data loss prevention rules, and mailbox delegation.
• Devices — Intune enrolment, compliance policies, and endpoint protection coverage.
• Threat protection — Microsoft Defender for Business configuration, safe links, and anti-phishing policies.

Weak authentication is the single most common finding. Only 40% of UK businesses have two-factor authentication enabled (DSIT 2025) (gov.uk Cyber Security Breaches Survey 2025), and most audits surface MFA gaps alongside dozens of other misconfigurations.

How does the M365 security audit work?

The audit runs in four stages over a few days, with no downtime for your staff. We start read-only, so nothing changes in your tenant until you have seen the findings and agreed what to fix.

1. Tenant access — we connect with read-only access to review configuration, policies and security settings. 2. Security assessment — we check Microsoft Secure Score, Conditional Access, MFA, DLP, sharing policies and admin configuration against best practice. 3. Risk report — you receive a prioritised report with risk ratings, plain-English explanations and specific remediation steps. 4. Remediation — we walk your team through the findings and either implement fixes directly or hand off clear instructions.

Because the assessment phase is read-only, it is non-disruptive — no policies change and no users are affected until remediation is scheduled.

Why do UK SMEs need an M365 security audit?

UK SMEs need an audit because Microsoft 365 is where the business actually lives — email, files, identities and Teams — and a single compromised account can reach all of it. Breaches are common and expensive, and most start with a credential or phishing gap an audit would have caught.

In the last year, 43% of UK businesses experienced a breach or attack (DSIT 2025), with the average disruptive breach costing £3,550 (gov.uk Cyber Security Breaches Survey 2025). The NCSC's small business guidance is clear that turning on MFA and removing legacy access are among the highest-value steps you can take — exactly what the audit verifies. For broader threat context, AMVIA's managed cybersecurity team monitors these tenants 24/7.

Microsoft also moves the goalposts. Defaults and features change often, so a configuration that was fine six months ago may now leave a gap — which is why audits work best as a recurring control, not a one-off.

In-house review vs an AMVIA M365 security audit

A busy internal IT team can check the obvious settings, but a benchmark-driven audit catches the gaps that defaults hide. The table below shows where a managed audit earns its place.

The audit also gives you documentation you can show auditors and insurers — useful when you need to evidence good practice for Cyber Essentials or cyber insurance renewals.

How much does an M365 security audit cost?

Pricing depends on tenant size and licence mix, and AMVIA quotes a fixed fee with no lock-in. The assessment is read-only and time-boxed; remediation is scoped separately once you have seen the prioritised findings, so you only pay to fix what matters.

Most organisations see a Secure Score increase of 30 to 50 points (a typical range across UK tenants we audit in 2026) after implementing audit recommendations, which is a measurable, repeatable way to show your security posture improving over time. For tenants that need ongoing control, the audit pairs naturally with our M365 hardening guide and MFA setup for Microsoft 365.

Why choose AMVIA for your M365 security audit?

AMVIA audits and secures Microsoft 365 for 1,200+ UK businesses across legal, finance, healthcare and professional services. We are a security partner, not a telecoms reseller — Microsoft-certified engineers who configure these controls daily and stand behind the fix.

• Cyber Essentials Plus certified and a Microsoft Solutions Partner (Modern Work, Security and Infrastructure).
• 1,200+ UK businesses secured, with critical issues responded to within one hour.
• UK-based engineers who understand UK compliance and the controls insurers and regulators look for.
• One accountable provider for the audit, the fixes and the ongoing monitoring.