Microsoft 365 Security
Most of the security incidents we respond to in Gloucestershire start the same way: a phishing email opens a session in someone’s Microsoft 365 account, and the attacker spends days inside an inbox before anyone notices. Microsoft 365 ships with strong building blocks — Defender, Conditional Access, Intune, Purview — but those features only protect the tenants where they are actually configured, monitored, and tied to a response process.
System Force IT runs Microsoft 365 security as a managed service for businesses across Gloucestershire and the surrounding counties. We harden the tenant against the techniques that actually compromise UK SMEs — token theft, MFA fatigue, OAuth consent grants, malicious inbox rules — and we keep watch so something flagged at 02:00 doesn’t become front-page news at 09:00.
What we secure inside Microsoft 365
Every Microsoft 365 tenant has six attack surfaces. We address each one with documented configuration, monitoring, and an escalation path.
Identity & access
Conditional Access policies, phishing-resistant MFA, named-locations enforcement, and tightened session lifetimes — reviewed quarterly against your actual sign-in logs, not a generic baseline.
Email & collaboration
Microsoft Defender for Office 365 tuned for your sender patterns, Safe Links and Safe Attachments enforced, anti-impersonation rules covering directors and finance, and hidden-rule detection on every mailbox.
Endpoint protection
Intune-managed devices with Defender for Endpoint, BitLocker, attack-surface-reduction rules, and patch compliance reporting — visible in a single console rather than buried in admin centres.
Data protection & backup
Purview retention and DLP for the data classes you actually handle, plus a third-party backup of Exchange, SharePoint, OneDrive and Teams — because Microsoft’s SLA does not commit to restoring deleted user data.
App & OAuth governance
Restrict third-party app consent so a single phished click can’t hand a long-lived OAuth token to an attacker. We audit every existing app permission and revoke the unused ones.
Monitoring & response
Continuous alerting on impossible-travel sign-ins, mass downloads, mailbox forwarding rule changes, and suspicious admin activity — with a documented response runbook so action happens out of hours, not on Monday morning.
Why the Microsoft 365 defaults aren’t enough
A new Microsoft 365 tenant ships with sensible-but-loose defaults: Security Defaults are off in many older tenants, Conditional Access requires Azure AD P1, third-party app consent is permitted, and most baseline alerts route to an admin mailbox no one reads. Out of the box, a tenant looks “secure” while leaving the easiest attack paths open.
The compromises we’ve cleaned up across the last twelve months almost always involved one of three things: an attacker stealing a session token after a successful MFA prompt, an OAuth consent grant that gave a malicious app long-term mailbox access, or a hidden inbox rule auto-forwarding finance correspondence to an external address. None of those require the user to be careless — they require the tenant to be tightened.
A managed Microsoft 365 security service exists to do that tightening, keep it tightened as Microsoft introduces new features, and watch the things that go wrong in the meantime. We do that work continuously rather than as a one-off audit.
Why businesses choose System Force IT for Microsoft 365 security
30+ years of UK SME IT
We’ve been delivering managed IT to Gloucestershire businesses since the 1990s — long enough to have lived through several generations of email security.
Same-day response
Compromised accounts get an out-of-hours response, not a ticket queued for the next working day. Speed of response is what limits damage.
Microsoft Partner
Direct access to Microsoft escalation channels when an issue is genuinely on Microsoft’s side rather than yours.
Local engineers
UK-based, mostly Gloucestershire-based engineers who can be on-site if something needs hands-on attention. No offshore call centre handoffs.
Who we work with
Our Microsoft 365 security service is sized for businesses with 10 to 250 staff. The customers we work with are typically professional services firms, engineering and manufacturing companies, accountants, healthcare providers and architects — organisations where an email-borne incident wouldn’t just be inconvenient, it would be a regulatory event.
If you’re thinking about Cyber Essentials or already certified, our Microsoft 365 hardening covers the technical controls that scheme requires — access control, secure configuration, malware protection and patch management — with documented evidence ready for your annual reassessment. We can fold this work into a wider managed IT services engagement, or run it as a stand-alone Microsoft 365 security retainer.
Frequently asked questions
Do I need a separate licence for Microsoft 365 security features?
It depends which features. Conditional Access requires Azure AD Premium P1 (now Entra ID P1). Defender for Office 365 Plan 1 is included in Microsoft 365 Business Premium. We’ll review what your current licences entitle you to before recommending an upgrade — in many cases tenants are paying for features they aren’t using.
How long does a Microsoft 365 security review take?
A first-pass review of a typical 50-user tenant takes about a week of elapsed time and produces a written report. Implementing the recommended changes — without disrupting users — usually runs in parallel over the following month, with rollouts scheduled around your business hours.
Can you protect us against a phishing attack that bypasses MFA?
No single control stops every attack, but the layered approach genuinely works. Conditional Access enforcing trusted devices and locations, phishing-resistant MFA methods, and continuous session monitoring together stop the great majority of token-theft attacks. When something does get through, our monitoring catches it within minutes, not days.
What happens if you detect a compromised account out of hours?
High-severity alerts — impossible-travel sign-ins from unfamiliar countries, mass-download patterns, new external auto-forward rules — trigger an immediate response from our on-call team. We disable the affected account, revoke active sessions and OAuth tokens, then call you. This isn’t a 9-to-5 service.
Do you back up Microsoft 365 mailboxes and SharePoint?
Yes — and we recommend you don’t skip this. Microsoft’s SLA covers their own service availability, not user-deleted data, retention-policy expiry, or ransomware encryption of OneDrive content. We use a third-party backup that covers Exchange, SharePoint, OneDrive and Teams, with point-in-time restore.
Can you work alongside our existing IT provider?
Yes. Microsoft 365 security is one of those areas where co-managed engagements work well — we take responsibility for the tenant configuration and monitoring while your existing team handles end-user support. We’ll set up clear escalation rules so handovers don’t fall through the gaps.
Get a free Microsoft 365 security review
A 30-minute call, a read-only look at your tenant, and a written report covering the gaps we found and how to close them. No obligation, no follow-up sales pressure.
Or call us on 0330 0167 681