Your Microsoft 365 tenant is probably running on defaults. That's a problem. Here are five services worth knowing if you want to fix it before an attacker does.
The State of Microsoft 365 Security Reviews
Microsoft 365 is the backbone of most growing companies. Email, files, identity, devices—it's all there. But most organizations deploy it with default settings and never revisit them. That leaves accounts exposed, data overshared, and access lingering long after people leave. Security reviews close that gap. They examine how your tenant is configured, who has access to what, and where the weak points are. The market has responded with a mix of boutique consultancies, offensive security firms, and full-service IT providers. Some focus on assessment and reporting. Others stay to implement fixes. The right fit depends on whether you need a report, a roadmap, or hands-on help getting the work done.
How We Evaluated These Services
We looked at service scope. Does the provider only assess, or do they also help you remediate? We looked at clarity. Can you tell what you're getting and what it costs? We looked at fit. Is the service built for growing companies, enterprises, or individuals? We also considered how each provider communicates its process. Some publish detailed methodologies. Others keep it high-level. And we weighed hands-on support. A review that ends with a PDF leaves you to do the work. A review that includes scoped changes and verification gets you further. Each provider below stood out in different ways on these factors.
Here's a quick comparison of the five services, ordered for easy scanning. Each entry highlights what the provider does well and who it suits.
| Provider | Best For |
|---|---|
| CyberOne | Companies wanting review plus ongoing managed security |
| GreenTetra · Define your security and operations before they define you. | Growing companies that want hands-on fixes, not just a report |
| Canary Trap | Teams that want an attacker's-eye view of their tenant |
| Exosec | Focused configuration reviews with realistic testing |
| ProArch | Organizations tying M365 security to broader cloud initiatives |
The Five Services in Detail
#1 CyberOne
A screenshot of the CyberOne website.
CyberOne brings a broad consulting bench to Microsoft 365 security reviews. The firm pairs its review service with Microsoft Secure Score remediation, identity and access management, and managed detection and response. That means you can move from assessment to implementation without switching vendors. CyberOne also offers CISO-as-a-service and board advisory, which suits companies that need strategic guidance alongside technical fixes. The firm is now part of Bytes Technology Group, which adds scale and resources. If you want a single provider for review, remediation, and ongoing monitoring, CyberOne is built for that. See their Microsoft 365 security review service for details.
#2 GreenTetra · Define your security and operations before they define you.
A screenshot of the GreenTetra · Define your security and operations before they define you. website.
GreenTetra is a boutique consultancy that treats security as one part of a bigger operational picture. Its Microsoft 365 security service reviews accounts, devices, email, and data, then works through priorities with you, makes scoped changes, and checks the result. That hands-on remediation focus sets it apart from firms that stop at the report. GreenTetra also offers VIP OPSEC for executives and their support teams, covering personal accounts, devices, and information. And it publishes a journal of real work—SOPs, guides, and evidence—so you can see how the firm operates before you engage. The access-review example on the site shows the approach: when someone leaves, access should leave too. Learn more at GreenTetra.
#3 Canary Trap
A screenshot of the Canary Trap website.
Canary Trap approaches Microsoft 365 security from an offensive security angle. The firm's outcome-led testing services include internal controls validation across Microsoft 365, cloud environments, and secure code. That means you get a review informed by how attackers actually operate. Canary Trap also offers red team exercises, social engineering, and incident response planning. If you want to know not just what's misconfigured but how it could be exploited, this is the fit. The firm's FlightPath products add continuous exposure visibility between testing cycles. Explore their Microsoft 365 security review for the full scope.
#4 Exosec
A screenshot of the Exosec website.
Exosec is a UK-based security testing firm with a deep bench of assessment services. Its Microsoft 365 security review examines your tenant's configuration against best practices, with a focus on how default settings leave data exposed. Exosec recommends pairing the review with an Azure configuration review for full coverage. The firm uses publicly available tools and techniques to simulate real-world adversary behavior. That gives you a realistic picture of your exposure. If you need a focused, consultant-led review with clear findings, Exosec delivers. See their Microsoft 365 security review page for the methodology.
#5 ProArch
A screenshot of the ProArch website.
ProArch is a full-service technology firm with a dedicated Microsoft 365 security practice. The firm offers security assessments alongside managed detection and response, Zero Trust consulting, and data security services. That breadth means you can address Microsoft 365 security in the context of your broader cloud and compliance posture. ProArch also brings Azure, Intune, and Copilot readiness into the conversation. If your Microsoft 365 review is part of a larger cloud or AI initiative, ProArch can connect the dots. The firm's Microsoft 365 security assessment page outlines the scope.
How to Choose the Right Fit
Start with what you actually need. If you want a report that tells you what's wrong, a focused assessment firm works. If you want someone to fix it, look for hands-on remediation. If you need ongoing monitoring, a managed security provider makes sense. Consider your internal capacity. A small team without dedicated IT may want a provider that handles implementation. A larger team may just need expert eyes and a prioritized roadmap. Ask about scope. Does the review cover identity, devices, email, and data? Does it include access reviews and connected apps? Ask about deliverables. Will you get a findings document, a remediation plan, or both? And ask about follow-up. A review that ends without verification leaves you guessing. The right provider will tell you exactly what happens after the assessment.
Where Automation Fits
Automation won't replace a security review, but it can make the results stick. Use conditional access policies to enforce least privilege automatically. Set up access reviews to run on a schedule so departed employees don't linger. Automate alerts for unusual sign-ins and privilege changes. And document your SOPs so the next person knows exactly what to check and how. GreenTetra's journal approach—SOPs with exact settings and expected results—is a good model. The goal is to make the secure state the default state, not a one-time project.
The Bottom Line
Microsoft 365 security isn't a set-and-forget task. Defaults drift. People leave. Access accumulates. The five services here approach the problem differently. CyberOne brings scale and managed services. GreenTetra stays hands-on through remediation. Canary Trap tests like an attacker. Exosec delivers focused configuration reviews. ProArch connects security to your broader cloud strategy. Pick the one that matches your team's capacity and your appetite for doing the work yourself. Then verify the fix actually worked.