Applied Cybernetics Group
T1564.008 Email Hiding Rules
- Technique
T1564.008- Tactics
- Defense Evasion
- Research, 90 days
- 1
- KEV CVEs mapped
- 0
- SigmaHQ rules
- 4
- Elastic, Splunk
- 5
- thrunt rules
- 0
- Upstream
- https://attack.mitre.org/techniques/T1564/008
MITRE description
Adversaries may use email rules to hide inbound emails in a compromised user's mailbox. Many email clients allow users to create inbox rules for various email functions, including moving emails to other folders, marking emails as read, or deleting emails. Rules may be created or modified within email clients or through external features such as the <code>New-InboxRule</code> or <code>Set-InboxRule</code> [PowerShell](https://attack.mitre.org/techniques/T1059/001) cmdlets on Windows systems.(Citation: Microsoft Inbox Rules)(Citation: MacOS Email Rules)(Citation: Microsoft New-InboxRule)(Citation: Microsoft Set-InboxRule) Adversaries may utilize email rules within a compromised user's mailbox to delete and/or move emails to less noticeable folders. Adversaries may do this to hide security alerts, C2 communication, or responses to [Internal Spearphishing](https://attack.mitre.org/techniques/T1534) emails sent from the compromised account. Any user or administrator within the organization (or adversary with valid credentials) may be able to create rules to automatically move or delete emails. These rules can be abused to impair/delay detection had the email content been immediately seen by a user or defender. Malicious rules commonly filter out emails based on key words (such as <code>malware</code>, <code>suspicious</code>, <code>phish</code>, and <code>hack</code>) found in message bodies and subject lines.(Citation: Microsoft Cloud App Security) In some environments, administrators may be able to enable email rules that operate organization-wide rather than on individual inboxes. For example, Microsoft Exchange supports transport rules that evaluate all mail an organization receives against user-specified conditions, then performs a user-specified action on mail that adheres to those conditions.(Citation: Microsoft Mail Flow Rules 2023) Adversaries that abuse such features may be able to automatically modify or delete all emails related to specific topics (such as internal security incident notifications).
Research citing this technique
Reports and advisories from the last 90 days that cite this technique.
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2026-10-22Huntress: M365 Token Spray and Replay Campaign Compromises Business Email Accounts
Detection coverage
SigmaHQ community rules
- Mail Forwarding/Redirecting Activity In O365 (threat-hunting)
- Inbox Rules Creation Or Update Activity in O365 (threat-hunting)
- Mail Forwarding/Redirecting Activity Via ExchangePowerShell Cmdlet (threat-hunting)
- Inbox Rules Creation Or Update Activity Via ExchangePowerShell Cmdlet (threat-hunting)
Elastic and Splunk rules
- M365 Exchange Inbox Rule with Obfuscated Name (elastic)
- M365 Exchange Inbox Phishing Evasion Rule Created (elastic)
- O365 BEC Email Hiding Rule Created (splunk)
- O365 Email New Inbox Rule Created (splunk)
- O365 Email Transport Rule Changed (splunk)