Hooking

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Hooking
Technique
ID T1179
Tactic Credential Access, Persistence, Privilege Escalation
Platform Windows
Permissions Required Administrator, SYSTEM
Data Sources API monitoring, Binary file metadata, DLL monitoring, Loaded DLLs, Process Monitoring, Windows event logs

Windows processes often leverage application programming interface (API) functions to perform tasks that require reusable system resources. Windows API functions are typically stored in dynamic-link libraries (DLLs) as exported functions. Hooking involves redirecting calls to these functions and can be implemented via:

  • Hooks procedures, which intercept and execute designated code in response to events such as messages, keystrokes, and mouse inputs.12
  • Import address table (IAT) hooking, which use modifications to a process’s IAT, where pointers to imported API functions are stored.234
  • Inline hooking, which overwrites the first bytes in an API function to redirect code flow.254

Similar to Process Injection, adversaries may use hooking to load and execute malicious code within the context of another process, masking the execution while also allowing access to the process's memory and possibly elevated privileges. Installing hooking mechanisms may also provide Persistence via continuous invocation when the functions are called through normal use.

Malicious hooking mechanisms may also capture API calls that include parameters that reveal user authentication credentials for Credential Access.6

Hooking is commonly utilized by Rootkits to conceal files, processes, Registry keys, and other objects in order to hide malware and associated behaviors.7

Examples

  • PLATINUM is capable of using Windows hook interfaces for information gathering such as credential access.8
  • FinFisher hooks processes by modifying IAT pointers to CreateWindowEx.2

Mitigation

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of operating system design features. For example, mitigating all hooking will likely have unintended side effects, such as preventing legitimate software (i.e., security products) from operating properly. Efforts should be focused on preventing adversary tools from running earlier in the chain of activity and on identifying subsequent malicious behavior.

Detection

Monitor for calls to the SetWindowsHookEx and SetWinEventHook functions, which install a hook procedure.19 Also consider analyzing hook chains (which hold pointers to hook procedures for each type of hook) using tools 91011 or by programmatically examining internal kernel structures.1213

Rootkits detectors 14 can also be used to monitor for various flavors of hooking activity.

Verify integrity of live processes by comparing code in memory to that of corresponding static binaries, specifically checking for jumps and other instructions that redirect code flow. Also consider taking snapshots of newly started processes 15 to compare the in-memory IAT to the real addresses of the referenced functions.163

Analyze process behavior to determine if a process is performing actions it usually does not, such as opening network connections, reading files, or other suspicious actions that could relate to post-compromise behavior.

References