|Data Sources||File monitoring, Windows registry, API monitoring|
Adversaries may hook into application programming interface (API) functions used by processes to redirect calls for persistent 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.1
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’s IAT, where pointers to imported API functions are stored.2
- Stuxnet modifies the Import Address Tables DLLs to hook specific APIs that are used to open project files.2
- Restrict Library Loading - Restrict the use of untrusted or unknown libraries, such as remote or unknown DLLs.
- Audit - Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses. Perform periodic integrity checks of the device to validate the correctness of the firmware, software, programs, and configurations. Integrity checks, which typically include cryptographic hashes or digital signatures, should be compared to those obtained at known valid states, especially after events like device reboots, program downloads, or program restarts.