huntrule

Windows Registry Set—Custom Outlook Today Page for Persistence

Flags registry writes that configure a custom Outlook Today URL using Outlook Today registry values.

FreeReviewedSigma · High · v1
Product
windows
Category
registry_set
Author
Tobias Michalski (Nextron Systems), David Bertho (@dbertho) & Eirik Sveen (@0xSV1), Storebrand (SigmaHQ), DRL 1.1
Published
2021-06-10
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Persistence → Defense Evasion

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule identifies registry changes under the Office Outlook Today location that indicate a custom “Today” page may be configured for persistence. Attackers can use registry values such as URL and UserDefinedUrl (and a Stamp flag) to point Outlook Today to an attacker-controlled or arbitrary web page. It relies on Windows registry_set telemetry, matching TargetObject paths and value name/suffix patterns while excluding events tied to ClickToRun installation executables.

Reporting behind it

Related detections9 linkedT1112 — drag to rearrange
Suspicious Registry Value under Console WindowsUpdates for C2 Storage
Suspicious Office VBA Object Model Access Enabled via Registry (via registry_set)
Suspicious PowerShell Payload Staging in HKCU Printers Registry Key
Suspicious Rootkit Configuration Registry Keys (via registry_set)
Suspicious Disabling of Chromium App-Bound Encryption via Policy Registry Key (via registry_set)
Windows reg.exe Registry Tampering of Internal Tool and Explorer Policy Settings (T1112)
Suspicious Disabling of Restricted Admin Mode via Registry (via registry_set)
Malicious WDigest UseLogonCredential Enabled for Cleartext Credential Theft (via registry_set)
Suspicious ClickFix RunMRU Entry Recording LOLBIN Command from Run Dialog
Windows Registry Set—Custom Outlook Today Page for Persistence
Pivot detection · T1112 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.