Windows processes often leverage these API functions to perform tasks that require reusable system resources. Windows API functions are typically stored in dynamic-link libraries (DLLs) as exported functions. One type of hooking seen in ICS involves redirecting calls to these functions via import address table (IAT) hooking. Stuxnet modifies the Import Address Tables DLLs to hook specific APIs that are used to open project files. Triton’s injector changes the function pointer of the ‘get main processor diagnostic data’ TriStation command to the address of imain.bin.”]
Source: https://collaborate.mitre.org/attackics/index.php/Technique/T0874