Core Compute & Isolation
Hyper-V & Cerberus Chip
A hardened Hyper-V underneath, with the Cerberus root-of-trust attesting firmware at boot so an implant below the OS cannot survive unnoticed. Solid, and — as with Nitro on AWS — not where your risk lives. No Azure tenant in the public record has been lost through the hypervisor. They are lost through consent grants, sync accounts and a service principal nobody owns.
Entra ID (Active Directory)
Entra ID is the whole game. Conditional Access is the most expressive policy engine any identity provider ships, and the expressiveness is the risk — policies interact, exclusions accumulate, and the break-glass account someone excluded during a 2023 outage is still excluded. Two structural facts to hold onto: the good controls (risk-based sign-in, Identity Protection, PIM) sit behind P1 and P2 licensing, so your security posture is a procurement decision made by someone else; and Entra ID is also the identity plane for Exchange, SharePoint and Teams, which means the blast radius of a tenant-level compromise is the business, not the infrastructure.
Under the Hood Architecture
Network Security Groups
VNets isolate by default; NSGs and Application Security Groups do the filtering. The part worth knowing before an incident is that NSG Flow Logs are off unless you turned them on, and coverage is not retroactive — enable them today and you learn nothing about last month. Ingestion into Sentinel is billed by volume, which is precisely why the sources that would have answered the question are the ones that got cut from the budget.
Defender for Identity
Sensors on the domain controllers themselves, flagging the classic on-premises attacks — Pass-the-Hash, Golden Ticket, DCSync — which is the detection layer any AD-focused engagement has to assume is present. It is also licensed separately and only sees what you deploy it to; a forgotten DC without the sensor is a blind spot that no dashboard reports as one.
Real-World Attack Surface
OMIGOD (Agent RCE)
Announced in September 2021, and the reason it matters more than its CVSS is the delivery: the OMI agent was installed silently on Linux VMs as a dependency of ordinary services such as Log Analytics and Automation. Customers who had never heard of OMI were running it, and the exploit was a single unauthenticated HTTP request with the auth header removed. The lesson generalises well beyond the patch — a managed platform installs software on your hosts on your behalf, and your asset inventory is only what you deployed, not what is running.
ChaosDB
The August 2021 Cosmos DB flaw, reached through the Jupyter Notebooks feature, exposed other tenants' primary keys and with them read and write access to their data. Two uncomfortable consequences. Tenant isolation in a managed data service is an assumption you cannot verify and cannot test. And because Cosmos DB primary keys are long-lived and rarely rotated, a key exposed then remains valid now unless someone acted — which is the real argument for moving off keys entirely.
Mandatory Hardening Baseline
- Audit Silent Agents: inventory the VM extensions actually present rather than the ones you meant to install, and block management ports (5985/5986) at the NSG. Enabling a platform feature installs an agent; that is the deal, and the only defence is knowing what is on the box.
- Cosmos DB Auth: move from primary access keys to Entra ID RBAC. A key is a bearer credential with no expiry, no identity and no per-request audit trail — once it leaks, use of it is indistinguishable from legitimate traffic, and rotating it means coordinating every consumer at once. That coordination cost is exactly why the migration keeps getting deferred.
- OAuth Consent Governance: turn off end-user consent and run an admin consent workflow instead. Illicit consent is the attack that beats MFA cleanly — the user authenticates correctly, approves an app, and the attacker holds a refresh token that survives a password reset. It shows up in no failed-login report. Accept the helpdesk load; the alternative is a mailbox being read for months.
Architecture Comparison
| Component | Azure | AWS |
|---|---|---|
| Isolation Architecture | Hyper-V + Cerberus chip | Nitro System |
| Network Visibility | NSG Flow Logs | VPC Flow Logs |
| Identity Security Tax | High (Entra ID P1/P2) | Moderate |
| Key Management | Key Vault / Managed HSM | KMS / CloudHSM |
