Ops Log tag
#Hardening
Reviewed Ops Log notes tagged Hardening, written by Michal Jatczak with source links, test context and operational checks.
6 reviewed notes
A Microsoft 365 DKIM CNAME target has two documented formats: read it per domain, never build it
Microsoft documents two DKIM CNAME target formats for Microsoft 365 custom domains, one ending in onmicrosoft.com and one in dkim.mail.microsoft. The page splits them by new versus existing custom domain and never mentions tenant age. Read each domain's values with Get-DkimSigningConfig.
Microsoft 365 E3 gained Defender Plan 1 in July and impersonation protection is still off by default
Microsoft 365 E3 has included Defender for Office 365 Plan 1 since 1 July 2026, but user and domain impersonation protection stays applied to nobody until an administrator configures it. This runbook gives the read-only check that settles whether anything in the tenant is actually enforcing it.
An empty Baseline scopes settings page proves nothing about the enforcement rollout
A Conditional Access policy targeting All resources with a resource exclusion now enforces on sign-ins requesting only baseline scopes, and the Baseline scopes settings page renders empty whether or not the rollout reached the tenant. Inventory the policy shape, the only part a read-only call can measure.
DMARC at p=none is not protection: what a deliverability check reads from public DNS
A DMARC record at p=none observes spoofing without blocking it. A free deliverability check reads SPF, DKIM, and DMARC from public DNS and tells you exactly which of those three is only watching. Here is how to run it and read it.
July 2026 Exchange Server security updates: confirm the build before removing the interim mitigation
The July 2026 Exchange SUs withdraw Microsoft's advice to keep the CVE-2026-42897 mitigation applied, but installing the update does not remove it. This note gives the per-SKU July build numbers, the PowerShell that reads the real SU level rather than the CU level, and the documented M2 rollback in an order that keeps the exposure window at zero, given that the code fix itself shipped in the June 2026 SU.
Fifteen Microsoft 365 tenant settings that need an explicit decision
Fifteen tenant-wide Microsoft 365 controls, each with the licence tier it actually needs, a read-only Graph, Exchange and SharePoint audit script, the side effects to plan for, and the rollback path. Six pieces of pre-2024 guidance in this area are corrected, five of them attached to numbered rows.