Should organisations prioritise device trust or collaboration hardening first in Microsoft 365?

Why device trust and collaboration hardening are linked in Microsoft 365

Microsoft 365 security decisions are often framed as a choice between trusted endpoints and safer collaboration settings, but that framing hides the real issue: both controls shape the same access path to documents, chats, mail, and shared workspaces. device trust reduces the likelihood that an untrusted endpoint can establish a useful session, while collaboration hardening limits what a session can do once it exists. Organisations that delay one side often leave the other side carrying too much risk. In practice, many security teams discover the larger gap only after data sharing or session abuse has already widened the blast radius.

For identity-adjacent collaboration platforms, this is especially important because access decisions are only half the problem. A device may be compliant and still leak data through permissive sharing, while a tightly controlled collaboration surface can still be reached from unmanaged devices if entry checks are weak. The operational question is not which control is “better” in the abstract, but which weakness is currently enabling the fastest route to sensitive data. Guidance from the OWASP Non-Human Identity Top 10 is useful here because it reinforces a broader principle: access paths matter most when control of entry and control of action are not aligned.

How the sequencing works in practice

In Microsoft 365, device trust is typically about the session entry conditions: whether the device is managed, compliant, enrolled, or otherwise allowed to satisfy access policy. Collaboration hardening is about what users can do after entry: sharing permissions, external collaboration, guest access, link behaviour, download restrictions, and the controls around mail, Teams, SharePoint, OneDrive, and sensitivity labels. The two are not interchangeable. A strong device posture does not stop oversharing, and a strong collaboration policy does not stop risky access from a compromised or unmanaged endpoint.

The practical sequencing depends on where your largest exposure sits. If unmanaged or weakly controlled endpoints are already reaching Microsoft 365, start with device trust because it closes the easiest entry route. If endpoint coverage is reasonably mature but the organisation still leaks data through overly permissive sharing and external collaboration, prioritise collaboration hardening because that is where exposure is multiplying. The most effective programmes usually narrow both surfaces in parallel, but they begin with the side that most directly reduces the current attack path.

• Use device trust to decide whether a session should be admitted at all.
• Use collaboration hardening to decide what a session may expose, forward, download, or share.
• Check whether guest access, link sharing, and unmanaged-device access are aligned to the same risk appetite.
• Verify that policy exceptions do not create a back door around the stricter control.

The guidance breaks down when policy intent, identity signals, and app-level sharing rules are managed by different teams without a common view of the actual data path.

Where the trade-off changes, and when the usual answer does not hold

Tighter device controls often increase friction for users and support teams, so organisations must balance access assurance against enrollment coverage, remote work demands, and legacy endpoints.

There is a genuine trade-off between reducing entry risk and reducing sharing risk. Device trust can be the faster win when unmanaged devices are numerous, but it may not meaningfully reduce exposure if privileged users can still exfiltrate data through approved sessions. Collaboration hardening can be the faster win when the problem is uncontrolled guest sharing or overexposed content, but it will not solve compromise of the endpoint itself. The right answer is therefore contextual, not ideological.

Where teams disagree is usually a sign that they are optimising different outcomes. Security operations may favour device trust because it reduces access noise and blocks risky sessions earlier, while collaboration owners may favour hardening because it directly limits data movement and external exposure. Both positions are valid, and the practical choice should follow the evidence of where the largest loss path exists today.

For Microsoft 365, the edge case is organisations with heavy external collaboration or rapid onboarding of unmanaged contractors. In those environments, collaboration hardening often deserves earlier attention because the business has already accepted broad access conditions and the remaining protection must come from how content is shared and retained. Conversely, highly regulated environments with strong collaboration controls but poor endpoint hygiene often need device trust first. The correct sequence is the one that collapses the shortest route from login to data access, not the one that sounds more mature on paper.

Risk and Threat Considerations

The material risk is that attackers or insiders exploit whichever side of the control stack is weakest. If device trust is weak, an unmanaged or compromised endpoint can still gain a productive session. If collaboration hardening is weak, a legitimate session can expose data through oversharing, external sharing, or permissive download and sync behaviour.

Failure mechanism: The exposure materialises when trust in the device does not sufficiently constrain session admission, or when collaboration settings allow content to flow beyond the intended audience. In recognised attack patterns, that combination supports initial access followed by data discovery and exfiltration through ordinary platform features rather than exotic exploitation.

Impact: Sensitive information can be accessed, copied, forwarded, or shared outside its intended boundary, and the organisation may lose visibility into which session or user actually enabled the leak. That turns a single weak control into a broad blast-radius problem across mail, files, chats, and shared workspaces.

Practitioner Guidance

What to prioritise: Start with the control gap that most directly shortens the path from login to data exposure. If unmanaged endpoints are the main weakness, prioritise device trust; if oversharing and guest exposure dominate, prioritise collaboration hardening.

Decision rule: If you can already prove that sessions are reaching sensitive content from poorly controlled devices, fix entry conditions first. If sessions are well governed but content is still spreading too freely, fix the sharing and collaboration layer first.

What practitioners underestimate: These controls fail most often when they are run as separate workstreams with separate success metrics. The useful metric is not “did we deploy both,” but whether the combined policy has reduced the fastest path to sensitive data.

Practitioner takeaway: Sequence the control that removes the biggest real-world blast radius first, then align the second control so it reinforces the same access boundary instead of creating a new exception path.

Related resources from NHI Mgmt Group

• Should organisations prioritise Zero Trust or least privilege first for NHI risk?
• When should organisations investigate Microsoft 365 application identities first?
• Should organisations prioritise zero trust or NHI governance first?
• What should organisations prioritise first: takeover response or inbox hardening?