> 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/external-email-with-a-single-internal-recipient-hidden-in-bcc.md).
# External email with a single internal recipient hidden in BCC
### 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 |
| ATT\&CK Tactic | Execution (TA0002), Credential Access (TA0006) |
| ATT\&CK Technique | User Execution (T1204), Brute Force: Password Cracking (T1110.002) |
| Severity | Informational |
### Description
External email with mailbox owner hidden in BCC as the only internal recipient.
### Attacker's Goals
BCC enables sending the same email to multiple hidden recipients without revealing them to each other.
### Investigative actions
* Review the headers and content for patterns or anomalies.
* Assess the email's context and attack techniques to determine the potential risk.
* Investigate if similar patterns have occurred recently across the organization.
### Variations
External email with only a hidden internal BCC recipient
**Synopsis**
| Field | Value |
| ----------------- | ------------------------------------------------------------------ |
| ATT\&CK Tactic | Execution (TA0002), Credential Access (TA0006) |
| ATT\&CK Technique | User Execution (T1204), Brute Force: Password Cracking (T1110.002) |
| Severity | Informational |
**Description**
External email with no visible recipients, mailbox owner is hidden in BCC.
**Attacker's Goals**
BCC enables sending the same email to multiple hidden recipients without revealing them to each other.
**Investigative actions**
* Review the headers and content for patterns or anomalies.
* Assess the email's context and attack techniques to determine the potential risk.
* Investigate if similar patterns have occurred recently across the organization.
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://cortex-docs.paloaltonetworks.com/analytics-alerts/alerts-by-name/external-email-with-a-single-internal-recipient-hidden-in-bcc.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.