System Binary Proxy Execution
Adversaries may bypass process and/or signature-based defenses by proxying execution of malicious content with signed, or otherwise trusted, binaries. Binaries used in this technique are often Microsoft-signed files, indicating that they have been either downloaded from Microsoft or are already native in the operating system.[1] Binaries signed with trusted digital certificates can typically execute on Windows systems protected by digital signature validation. Several Microsoft signed binaries that are default on Windows installations can be used to proxy execution of other files or commands.
Similarly, on Linux systems adversaries may abuse trusted binaries such as split to proxy execution of malicious commands.[2][3]
Procedure Examples
| ID | Name | Description |
|---|---|---|
| G0032 | Lazarus Group |
Lazarus Group lnk files used for persistence have abused the Windows Update Client ( |
Mitigations
| ID | Mitigation | Description |
|---|---|---|
| M1042 | Disable or Remove Feature or Program |
Many native binaries may not be necessary within a given environment. |
| M1038 | Execution Prevention |
Consider using application control to prevent execution of binaries that are susceptible to abuse and not required for a given system or network. |
| M1050 | Exploit Protection |
Microsoft's Enhanced Mitigation Experience Toolkit (EMET) Attack Surface Reduction (ASR) feature can be used to block methods of using using trusted binaries to bypass application control. |
| M1026 | Privileged Account Management |
Restrict execution of particularly vulnerable binaries to privileged accounts or groups that need to use it to lessen the opportunities for malicious usage. |
Detection
| ID | Data Source | Data Component | Detects |
|---|---|---|---|
| DS0017 | Command | Command Execution |
Monitor executed commands and arguments that may forge credential materials that can be used to gain access to web applications or Internet services. |
| DS0022 | File | File Creation |
Monitor for file activity (creations, downloads, modifications, etc.), especially for file types that are not typical within an environment and may be indicative of adversary activity. |
| DS0011 | Module | Module Load |
Monitor DLL/PE file events, specifically creation of these binary files as well as the loading of DLLs into processes. Look for DLLs that are not recognized or not normally loaded into a process. |
| DS0029 | Network Traffic | Network Connection Creation |
Monitor for newly constructed network connections that are sent or received by untrusted hosts. |
| DS0009 | Process | OS API Execution |
Monitor for API calls that bypass process and/or signature based defenses by proxying execution of malicious content with signed, or otherwise trusted, binaries. |
| Process Creation |
Monitor processes and command-line parameters for signed binaries that may be used to proxy execution of malicious files. Compare recent invocations of signed binaries that may be used to proxy execution with prior history of known good arguments and loaded files to determine anomalous and potentially adversarial activity. Legitimate programs used in suspicious ways, like msiexec.exe downloading an MSI file from the Internet, may be indicative of an intrusion. Correlate activity with other suspicious behavior to reduce false positives that may be due to normal benign use by users and administrators. |
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| DS0024 | Windows Registry | Windows Registry Key Modification |
Monitor for changes made to Windows Registry keys and/or values that may forge credential materials that can be used to gain access to web applications or Internet services. |