Description
Adversaries may abuse Microsoft Outlook rules to obtain persistence on a compromised system. Outlook rules allow a user to define automated behavior to manage email messages. A benign rule might, for example, automatically move an email to a particular folder in Outlook if it contains specific words from a specific sender. Malicious Outlook rules can be created that can trigger code execution when an adversary sends a specifically crafted email to that user.(Citation: SilentBreak Outlook Rules)
Once malicious rules have been added to the user’s mailbox, they will be loaded when Outlook is started. Malicious rules will execute when an adversary sends a specifically crafted email to the user.(Citation: SilentBreak Outlook Rules)
Platforms
Mitigations (2)
Update SoftwareM1051
For the Outlook methods, blocking macros may be ineffective as the Visual Basic engine used for these features is separate from the macro scripting engine.(Citation: SensePost Outlook Forms) Microsoft has released patches to try to address each issue. Ensure KB3191938 which blocks Outlook Visual Basic and displays a malicious code warning, KB4011091 which disables custom forms by default, and KB40
Behavior Prevention on EndpointM1040
On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent Office applications from creating child processes and from writing potentially malicious executable content to disk. (Citation: win10_asr)
Associated Software (1)
| ID | Name | Type | Context |
|---|---|---|---|
| S0358 | Ruler | Tool | [Ruler](https://attack.mitre.org/software/S0358) can be used to automate the abuse of Outlook Rules to establish persistence.(Citation: SensePost Rule... |
References
- Damian Pfammatter. (2018, September 17). Hidden Inbox Rules in Microsoft Exchange. Retrieved October 12, 2021.
- Fox, C., Vangel, D. (2018, April 22). Detect and Remediate Outlook Rules and Custom Forms Injections Attacks in Office 365. Retrieved February 4, 2019.
- Landers, N. (2015, December 4). Malicious Outlook Rules. Retrieved February 4, 2019.
- SensePost. (2017, September 21). NotRuler - The opposite of Ruler, provides blue teams with the ability to detect Ruler usage against Exchange. Retrieved February 4, 2019.
Frequently Asked Questions
What is T1137.005 (Outlook Rules)?
T1137.005 is a MITRE ATT&CK technique named 'Outlook Rules'. It belongs to the Persistence tactic(s). Adversaries may abuse Microsoft Outlook rules to obtain persistence on a compromised system. Outlook rules allow a user to define automated behavior to manage email messages. A benign rule might, for...
How can T1137.005 be detected?
Detection of T1137.005 (Outlook Rules) typically involves monitoring system logs, network traffic, and endpoint telemetry. Use SIEM rules, EDR solutions, and behavioral analytics to identify suspicious activity associated with this technique.
What mitigations exist for T1137.005?
There are 2 documented mitigations for T1137.005. Key mitigations include: Update Software, Behavior Prevention on Endpoint.
Which threat groups use T1137.005?
While specific threat group attribution may vary, this technique has been observed in various real-world attacks. Check the MITRE ATT&CK website for the latest threat intelligence.