> For the complete documentation index, see [llms.txt](https://cortex-docs.paloaltonetworks.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/unrecognized-internal-address-aad-mismatch.md).

# Unrecognized internal address (AAD mismatch)

### Synopsis

| Field                | Value                                  |
| -------------------- | -------------------------------------- |
| Activation Period    | 14 Days                                |
| Training Period      | 30 Days                                |
| Test Period          | N/A (single event)                     |
| Deduplication Period | 1 Hour 30 Minutes                      |
| Required Data        | Microsoft 365 Emails                   |
| Detection Modules    | Email                                  |
| Detector Tags        | Employee Impersonation, Spear Phishing |
| ATT\&CK Tactic       | Initial Access (TA0001)                |
| ATT\&CK Technique    | Phishing (T1566)                       |
| Severity             | Informational                          |

### Description

An email was received from an address using an internal domain, but the sender is not found in Active Directory. This may indicate an impersonation attempt or domain spoofing.

### Attacker's Goals

The attacker aims to impersonate an internal user to gain trust, bypass security controls, and potentially extract sensitive information or distribute malicious content through internal-looking emails.

### Investigative actions

* Verify if the sender address exists in Active Directory.
* Check historical email activity from the spoofed address.
* Review email headers for spoofing indicators (SPF, DKIM, DMARC failures).
* Identify if recipients engaged with the email (clicked links, downloaded attachments).
* Correlate with other alerts involving the same sender or domain.


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