Hooking

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Hooking
Technique
ID	T0874
Tactic	Execution, Privilege Escalation
Data Sources	File: File Modification, Module: Module Load
Asset	Engineering Workstation

Description

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.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

Procedure Examples

• Stuxnet modifies the Import Address Tables DLLs to hook specific APIs that are used to open project files.2
• Triton's injector, inject.bin, changes the function pointer of the 'get main processor diagnostic data' TriStation command to the address of imain.bin so that it is executed prior to the normal handler.3

Mitigations

• 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.

References

1. ^  Enterprise ATT&CK. (n.d.). Hooking. Retrieved October 27, 2019.
2. a b  Nicolas Falliere, Liam O Murchu, Eric Chien. (2011, February). W32.Stuxnet Dossier (Version 1.4). Retrieved September 22, 2017.

3. ^  Jos Wetzels. (2018, January 16). Analyzing the TRITON industrial malware. Retrieved October 22, 2019.