Adversaries may modify code signing policies to enable execution of unsigned or self-signed code. Code signing provides a level of authenticity on a program from a developer and a guarantee that the program has not been tampered with. Security controls can include enforcement mechanisms to ensure that only valid, signed code can be run on an operating system.
Some of these security controls may be enabled by default, such as Driver Signature Enforcement (DSE) on Windows or System Integrity Protection (SIP) on macOS.(Citation: Microsoft DSE June 2017)(Citation: Apple Disable SIP) Other such controls may be disabled by default but are configurable through application controls, such as only allowing signed Dynamic-Link Libraries (DLLs) to execute on a system. Since it can be useful for developers to modify default signature enforcement policies during the development and testing of applications, disabling of these features may be possible with elevated permissions.(Citation: Microsoft Unsigned Driver Apr 2017)(Citation: Apple Disable SIP)
Adversaries may modify code signing policies in a number of ways, including through use of command-line or GUI utilities, Modify Registry, rebooting the computer in a debug/recovery mode, or by altering the value of variables in kernel memory.(Citation: Microsoft TESTSIGNING Feb 2021)(Citation: Apple Disable SIP)(Citation: FireEye HIKIT Rootkit Part 2)(Citation: GitHub Turla Driver Loader) Examples of commands that can modify the code signing policy of a system include <code>bcdedit.exe -set TESTSIGNING ON</code> on Windows and <code>csrutil disable</code> on macOS.(Citation: Microsoft TESTSIGNING Feb 2021)(Citation: Apple Disable SIP) Depending on the implementation, successful modification of a signing policy may require reboot of the compromised system. Additionally, some implementations can introduce visible artifacts for the user (ex: a watermark in the corner of the screen stating the system is in Test Mode). Adversaries may attempt to remove such artifacts.(Citation: F-Secure BlackEnergy 2014)
To gain access to kernel memory to modify variables related to signature checks, such as modifying <code>g_CiOptions</code> to disable Driver Signature Enforcement, adversaries may conduct Exploitation for Privilege Escalation using a signed, but vulnerable driver.(Citation: Unit42 AcidBox June 2020)(Citation: GitHub Turla Driver Loader)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| PR.AA-05.02 | Privileged system access | Mitigates | T1553.006 | Code Signing Policy Modification |
Comments
This diagnostic statement protects against Code Signing Policy Modification through the use of privileged account management and the use of multi-factor authentication.
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| DE.CM-09.01 | Software and data integrity checking | Mitigates | T1553.006 | Code Signing Policy Modification |
Comments
This diagnostic statement protects against Code Signing Policy Modification through the use of verifying integrity of software/firmware, loading software that is trusted, ensuring privileged process integrity and checking software signatures.
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| PR.PS-01.03 | Configuration deviation | Mitigates | T1553.006 | Code Signing Policy Modification |
Comments
This diagnostic statement provides protection from Code Signing Policy Modification through the implementation of security configuration baselines for OS, software, file integrity monitoring and imaging. Security baselining and integrity checking can help protect against adversaries attempting to compromise and modify software and its configurations.
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| PR.IR-01.06 | Production environment segregation | Mitigates | T1553.006 | Code Signing Policy Modification |
Comments
This diagnostic statement provides protections for production environments. Measures such as network segmentation and access control reduce the attack surface, restrict movement by adversaries, and protect critical assets and data from compromise.
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| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| action.malware.variety.Disable controls | Disable or interfere with security controls | related-to | T1553.006 | Code Signing Policy Modification |
| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| alerts_for_windows_machines | Alerts for Windows Machines | technique_scores | T1553.006 | Code Signing Policy Modification |
Comments
This control can be used to monitor for the execution of commands that could modify the code signing policy of a system, such as bcdedit.exe -set TESTSIGNING ON.
References
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