> 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/exchange-email-hiding-inbox-rule.md).
# Exchange email-hiding inbox rule
### Synopsis
| Field | Value |
| -------------------- | ---------------------------------------------- |
| Activation Period | 14 Days |
| Training Period | 30 Days |
| Test Period | N/A (single event) |
| Deduplication Period | 1 Day |
| Required Data | Office 365 Audit |
| Detection Modules | Identity Threat Module, Email |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Hide Artifacts: Email Hiding Rules (T1564.008) |
| Severity | Informational |
### Description
A user configured an Exchange inbox rule that may be used to hide emails.
### Attacker's Goals
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
### Investigative actions
* Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
* Check if the rule keywords look suspicious.
* Investigate the IP address associated with the rule.
* Follow further actions done by the account.
* Check for a possible phishing campaign on the organization.
* Look for multiple instances of email hiding, which may be an indication of a larger campaign.
* Check if the user regularly configures inbox rules.
### Variations
Possible BEC Exchange email-hiding inbox rule
**Synopsis**
| Field | Value |
| ----------------- | ---------------------------------------------- |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Hide Artifacts: Email Hiding Rules (T1564.008) |
| Severity | Medium |
**Description**
A user configured an Exchange inbox rule that may be used to hide emails. The rule contains characteristics that resemble a business email compromise (BEC) attack.
**Attacker's Goals**
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
**Investigative actions**
* Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
* Check if the rule keywords look suspicious.
* Investigate the IP address associated with the rule.
* Follow further actions done by the account.
* Check for a possible phishing campaign on the organization.
* Look for multiple instances of email hiding, which may be an indication of a larger campaign.
* Check if the user regularly configures inbox rules.
Suspicious Exchange email-hiding inbox rule
**Synopsis**
| Field | Value |
| ----------------- | ---------------------------------------------- |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Hide Artifacts: Email Hiding Rules (T1564.008) |
| Severity | Medium |
**Description**
A user configured an Exchange inbox rule that may be used to hide emails. The rule hides emails that contain suspicious keywords, which may be a sign of a compromised account.
**Attacker's Goals**
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
**Investigative actions**
* Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
* Check if the rule keywords look suspicious.
* Investigate the IP address associated with the rule.
* Follow further actions done by the account.
* Check for a possible phishing campaign on the organization.
* Look for multiple instances of email hiding, which may be an indication of a larger campaign.
* Check if the user regularly configures inbox rules.
Abnormal Exchange email-hiding inbox rule
**Synopsis**
| Field | Value |
| ----------------- | ---------------------------------------------- |
| ATT\&CK Tactic | Defense Evasion (TA0005) |
| ATT\&CK Technique | Hide Artifacts: Email Hiding Rules (T1564.008) |
| Severity | Low |
**Description**
A user configured an Exchange inbox rule that may be used to hide emails.
**Attacker's Goals**
Prevent an organization from warning users that they've been compromised (e.g. an internal spear-phishing campaign).
**Investigative actions**
* Look for signs that the user account and mailbox are compromised (e.g. abnormal logins, unusual activity).
* Check if the rule keywords look suspicious.
* Investigate the IP address associated with the rule.
* Follow further actions done by the account.
* Check for a possible phishing campaign on the organization.
* Look for multiple instances of email hiding, which may be an indication of a larger campaign.
* Check if the user regularly configures inbox rules.
---
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