Adversaries may abuse the KernelCallbackTable of a process to hijack its execution flow in order to run their own payloads.[1][2] The KernelCallbackTable can be found in the Process Environment Block (PEB) and is initialized to an array of graphic functions available to a GUI process once user32.dll is loaded.[3]
An adversary may hijack the execution flow of a process using the KernelCallbackTable by replacing an original callback function with a malicious payload. Modifying callback functions can be achieved in various ways involving related behaviors such as Reflective Code Loading or Process Injection into another process.
A pointer to the memory address of the KernelCallbackTable can be obtained by locating the PEB (ex: via a call to the NtQueryInformationProcess() Native API function).[4] Once the pointer is located, the KernelCallbackTable can be duplicated, and a function in the table (e.g., fnCOPYDATA) set to the address of a malicious payload (ex: via WriteProcessMemory()). The PEB is then updated with the new address of the table. Once the tampered function is invoked, the malicious payload will be triggered.[1]
The tampered function is typically invoked using a Windows message. After the process is hijacked and malicious code is executed, the KernelCallbackTable may also be restored to its original state by the rest of the malicious payload.[1] Use of the KernelCallbackTable to hijack execution flow may evade detection from security products since the execution can be masked under a legitimate process.
| ID | Name | Description |
|---|---|---|
| S0182 | FinFisher |
FinFisher has used the |
| G0032 | Lazarus Group |
Lazarus Group has abused the |
| ID | Mitigation | Description |
|---|---|---|
| M1040 | Behavior Prevention on Endpoint |
Some endpoint security solutions can be configured to block some types of behaviors related to process injection/memory tampering based on common sequences of indicators (ex: execution of specific API functions). |
Analyze process behavior to determine if a process is performing actions it usually does not, such as opening network connections, reading files, or other suspicious behaviors that could relate to post-compromise behavior.
Monitoring Windows API calls indicative of the various types of code injection may generate a significant amount of data and may not be directly useful for defense unless collected under specific circumstances. for known bad sequence of calls, since benign use of API functions may be common and difficult to distinguish from malicious behavior. Windows API calls such as WriteProcessMemory() and NtQueryInformationProcess() with the parameter set to ProcessBasicInformation may be used for this technique.[1]