KernelCallbackTable

What the technique is

Adversaries may abuse the KernelCallbackTable of a process to hijack its execution flow in order to run their own payloads. 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. 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). 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. 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. […]

What MITRE says you would watch

• AN1593

  Unexpected modification of the KernelCallbackTable in a process’s PEB followed by invocation of modified callback functions (e.g., fnCOPYDATA) through Windows messages. Defender observes suspicious API call chains such as NtQueryInformationProcess → WriteProcessMemory → abnormal GUI callback execution, often correlating to anomalous process behavior such as network activity or code injection.