> 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/outbound-email-includes-an-external-bcc-recipient-observed-for-the-first-time.md).

# Outbound email includes an external BCC recipient observed for the first time

### Synopsis

| Field                | Value                                                              |
| -------------------- | ------------------------------------------------------------------ |
| Activation Period    | 14 Days                                                            |
| Training Period      | 30 Days                                                            |
| Test Period          | N/A (single event)                                                 |
| Deduplication Period | 1 Day                                                              |
| Required Data        | Microsoft 365 Emails                                               |
| Detection Modules    | Email                                                              |
| Detector Tags        | Exfiltration                                                       |
| ATT\&CK Tactic       | Execution (TA0002), Credential Access (TA0006)                     |
| ATT\&CK Technique    | User Execution (T1204), Brute Force: Password Cracking (T1110.002) |
| Severity             | Informational                                                      |

### Description

Internal sender BCC'd an external recipient whose address has not been observed in prior communications.

### Attacker's Goals

Use BCC to covertly exfiltrate data to an unusual external recipient without visibility to other recipients or monitoring systems.

### Investigative actions

* Review headers and content for anomalies or potential exposure of sensitive data.
* Assess the email's context and attack techniques to determine the potential risk.
* Investigate if similar patterns have occurred recently across the organization.

### Variations

<details>

<summary>Outbound email sent to an unknown external BCC recipient with no To or CC addresses</summary>

**Synopsis**

| Field             | Value                                                              |
| ----------------- | ------------------------------------------------------------------ |
| ATT\&CK Tactic    | Execution (TA0002), Credential Access (TA0006)                     |
| ATT\&CK Technique | User Execution (T1204), Brute Force: Password Cracking (T1110.002) |
| Severity          | Low                                                                |

**Description**

Internal sender BCC'd an external recipient whose address has not been observed in prior communications.

**Attacker's Goals**

Use BCC to covertly exfiltrate data to an unusual external recipient without visibility to other recipients or monitoring systems.

**Investigative actions**

* Review headers and content for anomalies or potential exposure of sensitive data.
* Assess the email's context and attack techniques to determine the potential risk.
* Investigate if similar patterns have occurred recently across the organization.

</details>


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