Adversaries may hook into application programming interface (API) functions used by processes to redirect calls for execution and privilege escalation means. 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. (Citation: Enterprise ATT&CK)
Adversaries may hook into application programming interface (API) functions used by processes to redirect calls for execution and privilege escalation means. 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. (Citation: Enterprise ATT&CK)
One type of hooking seen in ICS involves redirecting calls to these functions via import address table (IAT) hooking. IAT hooking uses modifications to a process IAT, where pointers to imported API functions are stored. (Citation: Nicolas Falliere, Liam O Murchu, Eric Chien February 2011)
Adversaries may utilize hooking to hide the presence of artifacts associated with their behaviors to evade detection. Hooking can be used to modify return values or data structures of system APIs and function calls. This process typically involves using 3rd party root frameworks, such as Xposed or Magisk, with either a system exploit or pre-existing root access. By including custom modules for root frameworks, adversaries can hook system APIs and alter the return value and/or system data structures to alter functionality/visibility of various aspects of the system.