M. Visser
63c1f47689
* Added OWA (outlook for web) new AppID
**Title:** Add new Outlook for Web AppID to abnormal Microsoft 365 ClientAppID rule
**Description:**
This pull request updates the `initial_access_microsoft_365_abnormal_clientappid` rule to include the newly introduced Outlook for Web AppID:
- **New AppID**: `9199bf20-a13f-4107-85dc-02114787ef48`
### Context
Outlook for Web (OWA) is migrating to a new authentication platform using MSAL and a Single Page Application (SPA) auth model. As part of this backend change, Microsoft is replacing the existing OWA AppID with a new one. This change is being rolled out during the first half of calendar year 2024, with full deployment expected by Q4 2024.
- **Old OWA AppID**: `00000002-0000-0ff1-ce00-000000000000`
- **New OWA AppID**: `9199bf20-a13f-4107-85dc-02114787ef48`
Although no action is required for tenant administrators, this new AppID may show up in logs and should be accounted for in detections relying on known legitimate ClientAppIDs.
### Why this change?
The rule `initial_access_microsoft_365_abnormal_clientappid` flags potentially suspicious or unauthorized client applications accessing Microsoft 365 services. To prevent false positives caused by this official change from Microsoft, this PR adds the new OWA AppID to the allowlist.
### References
- Microsoft 365 Message Center notice (ref: MC715025)
- [MSAL documentation](https://learn.microsoft.com/en-us/azure/active-directory/develop/msal-overview)
* Update initial_access_microsoft_365_abnormal_clientappid.toml
Updated updated_date
rules/
Rules within this folder are organized by solution or platform. The structure is flattened out, because nested file hierarchies are hard to navigate and find what you're looking for. Each directory contains several .toml files, and the primary ATT&CK tactic is included in the file name when it's relevant (i.e. windows/execution_via_compiled_html_file.toml)
| folder | description |
|---|---|
. |
Root directory where rules are stored |
apm/ |
Rules that use Application Performance Monitoring (APM) data sources |
cross-platform/ |
Rules that apply to multiple platforms, such as Windows and Linux |
integrations/ |
Rules organized by Fleet integration |
linux/ |
Rules for Linux or other Unix based operating systems |
macos/ |
Rules for macOS |
ml/ |
Rules that use machine learning jobs (ML) |
network/ |
Rules that use network data sources |
promotions/ |
Rules that promote external alerts into detection engine alerts |
windows/ |
Rules for the Microsoft Windows Operating System |
Integration specific rules are stored in the integrations/ directory:
| folder | integration |
|---|---|
aws/ |
Amazon Web Services (AWS) |
azure/ |
Microsoft Azure |
cyberarkpas/ |
Cyber Ark Privileged Access Security |
endpoint/ |
Elastic Endpoint Security |
gcp/ |
Google Cloud Platform (GCP) |
google_workspace/ |
Google Workspace (formerly GSuite) |
o365/ |
Microsoft Office |
okta/ |
Oka |