> 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.
---
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