| ID | Name |
|---|---|
| T1553.001 | Gatekeeper Bypass |
| T1553.002 | Code Signing |
| T1553.003 | SIP and Trust Provider Hijacking |
| T1553.004 | Install Root Certificate |
| T1553.005 | Mark-of-the-Web Bypass |
| T1553.006 | Code Signing Policy Modification |
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.[1][2] 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.[3][2]
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.[4][2][5][6] Examples of commands that can modify the code signing policy of a system include bcdedit.exe -set TESTSIGNING ON on Windows and csrutil disable on macOS.[4][2] 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.[7]
To gain access to kernel memory to modify variables related to signature checks, such as modifying g_CiOptions to disable Driver Signature Enforcement, adversaries may conduct Exploitation for Privilege Escalation using a signed, but vulnerable driver.[8][6]
| ID | Name | Description |
|---|---|---|
| G0087 | APT39 |
APT39 has used malware to turn off the |
| S0089 | BlackEnergy |
BlackEnergy has enabled the |
| S0009 | Hikit |
Hikit has attempted to disable driver signing verification by tampering with several Registry keys prior to the loading of a rootkit driver component.[5] |
| S0664 | Pandora |
Pandora can use CVE-2017-15303 to disable Windows Driver Signature Enforcement (DSE) protection and load its driver.[10] |
| G0010 | Turla |
Turla has modified variables in kernel memory to turn off Driver Signature Enforcement after exploiting vulnerabilities that obtained kernel mode privileges.[8][6] |
| ID | Mitigation | Description |
|---|---|---|
| M1046 | Boot Integrity |
Use of Secure Boot may prevent some implementations of modification to code signing policies.[4] |
| M1026 | Privileged Account Management |
Limit the usage of local administrator and domain administrator accounts to be used for day-to-day operations that may expose them to potential adversaries. |
| M1024 | Restrict Registry Permissions |
Ensure proper permissions are set for the Registry to prevent users from modifying keys related to code signing policies. |
| ID | Data Source | Data Component |
|---|---|---|
| DS0017 | Command | Command Execution |
| DS0009 | Process | Process Creation |
| DS0024 | Windows Registry | Windows Registry Key Modification |
Monitor processes and command-line arguments for actions that could be taken to modify the code signing policy of a system, such as bcdedit.exe -set TESTSIGNING ON.[4] Consider monitoring for modifications made to Registry keys associated with code signing policies, such as HKCU\Software\Policies\Microsoft\Windows NT\Driver Signing. Modifications to the code signing policy of a system are likely to be rare.