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Input Capture: Credential API Hooking

ID Name
T1056.001 Keylogging
T1056.002 GUI Input Capture
T1056.003 Web Portal Capture
T1056.004 Credential API Hooking

Adversaries may hook into Windows application programming interface (API) functions and Linux system functions to collect user credentials. Malicious hooking mechanisms may capture API or function calls that include parameters that reveal user authentication credentials.[1] Unlike Keylogging, this technique focuses specifically on API functions that include parameters that reveal user credentials.

In Windows, 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.[2][3]
  • Import address table (IAT) hooking, which use modifications to a process’s IAT, where pointers to imported API functions are stored.[3][4][5]
  • Inline hooking, which overwrites the first bytes in an API function to redirect code flow.[3][6][5]

In Linux and macOS, adversaries may hook into system functions via the LD_PRELOAD (Linux) or DYLD_INSERT_LIBRARIES (macOS) environment variables, which enables loading shared libraries into a program’s address space. For example, an adversary may capture credentials by hooking into the libc read function leveraged by SSH or SCP.[7]

ID: T1056.004
Sub-technique of:  T1056
ⓘ
Platforms: Linux, Windows, macOS
Version: 1.2
Created: 11 February 2020
Last Modified: 15 April 2025
Version Permalink

Procedure Examples

ID Name Description
S0484 Carberp

Carberp has hooked several Windows API functions to steal credentials.[8]
S0363 Empire

Empire contains some modules that leverage API hooking to carry out tasks, such as netripper.[9]
S0182 FinFisher

FinFisher hooks processes by modifying IAT pointers to CreateWindowEx.[10][3]
S0353 NOKKI

NOKKI uses the Windows call SetWindowsHookEx and begins injecting it into every GUI process running on the victim's machine.[11]
G0068 PLATINUM

PLATINUM is capable of using Windows hook interfaces for information gathering such as credential access.[12]
S0416 RDFSNIFFER

RDFSNIFFER hooks several Win32 API functions to hijack elements of the remote system management user-interface.[13]
S0266 TrickBot

TrickBot has the ability to capture RDP credentials by capturing the CredEnumerateA API[14]

S0386 Ursnif

Ursnif has hooked APIs to perform a wide variety of information theft, such as monitoring traffic from browsers.[15]
S1154 VersaMem

VersaMem hooked and overrided Versa's built-in authentication method, setUserPassword, to intercept plaintext credentials when submitted to the server.[16]
S0251 Zebrocy

Zebrocy installs an application-defined Windows hook to get notified when a network drive has been attached, so it can then use the hook to call its RecordToFile file stealing method.[17]
S0330 Zeus Panda

Zeus Panda hooks processes by leveraging its own IAT hooked functions.[18]
S0412 ZxShell

ZxShell hooks several API functions to spawn system threads.[19]

Mitigations

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.

Detection

ID Data Source Data Component Detects
DS0017 Command Command Execution

Monitor executed commands and arguments associated with modifications to variables and files associated with loading shared libraries such as LD_PRELOAD on Linux and DYLD_INSERT_LIBRARIES on macOS.
DS0022 File File Creation

Monitor for newly constructed files that are added to absolute paths of shared libraries such as LD_PRELOAD on Linux (such as /etc/ld.so.preload) and DYLD_INSERT_LIBRARIES on macOS.
File Modification

Monitor for changes to files associated with loading shared libraries such as LD_PRELOAD on Linux (such as /etc/ld.so.preload) and DYLD_INSERT_LIBRARIES on macOS.
DS0011 Module Module Load

Monitor library metadata, such as a hash, and compare libraries that are loaded at process execution time against previous executions to detect differences that do not correlate with patching or updates.

DS0009 Process OS API Execution

Monitor for API calls to the SetWindowsHookEx and SetWinEventHook functions, which install a hook procedure.[2][20] Also consider analyzing hook chains (which hold pointers to hook procedures for each type of hook) using tools[20][21][22] or by programmatically examining internal kernel structures.[23][24]
Process Metadata

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.

References

  1. Microsoft. (2017, September 15). TrojanSpy:Win32/Ursnif.gen!I. Retrieved December 18, 2017.
  2. Microsoft. (n.d.). Hooks Overview. Retrieved December 12, 2017.
  3. Hosseini, A. (2017, July 18). Ten Process Injection Techniques: A Technical Survey Of Common And Trending Process Injection Techniques. Retrieved December 7, 2017.
  4. Tigzy. (2014, October 15). Userland Rootkits: Part 1, IAT hooks. Retrieved December 12, 2017.
  5. Hillman, M. (2015, August 8). Dynamic Hooking Techniques: User Mode. Retrieved December 20, 2017.
  6. Mariani, B. (2011, September 6). Inline Hooking in Windows. Retrieved November 17, 2024.
  7. Joakim Kennedy and The BlackBerry Threat Research & Intelligence Team. (2022, June 9). Symbiote Deep-Dive: Analysis of a New, Nearly-Impossible-to-Detect Linux Threat. Retrieved March 24, 2025.
  8. Giuliani, M., Allievi, A. (2011, February 28). Carberp - a modular information stealing trojan. Retrieved September 12, 2024.
  9. Schroeder, W., Warner, J., Nelson, M. (n.d.). Github PowerShellEmpire. Retrieved April 28, 2016.
  10. FinFisher. (n.d.). Retrieved September 12, 2024.
  11. Grunzweig, J., Lee, B. (2018, September 27). New KONNI Malware attacking Eurasia and Southeast Asia. Retrieved November 5, 2018.
  12. Windows Defender Advanced Threat Hunting Team. (2016, April 29). PLATINUM: Targeted attacks in South and Southeast Asia. Retrieved February 15, 2018.
  1. Carr, N, et all. (2019, October 10). Mahalo FIN7: Responding to the Criminal Operators’ New Tools and Techniques. Retrieved October 11, 2019.
  2. Llimos, N., Pascual, C.. (2019, February 12). Trickbot Adds Remote Application Credential-Grabbing Capabilities to Its Repertoire. Retrieved March 12, 2019.
  3. Caragay, R. (2015, March 26). URSNIF: The Multifaceted Malware. Retrieved June 5, 2019.
  4. Black Lotus Labs. (2024, August 27). Taking The Crossroads: The Versa Director Zero-Day Exploitaiton. Retrieved August 27, 2024.
  5. Kaspersky Lab's Global Research & Analysis Team. (2018, February 20). A Slice of 2017 Sofacy Activity. Retrieved November 27, 2018.
  6. Ebach, L. (2017, June 22). Analysis Results of Zeus.Variant.Panda. Retrieved November 5, 2018.
  7. Allievi, A., et al. (2014, October 28). Threat Spotlight: Group 72, Opening the ZxShell. Retrieved September 24, 2019.
  8. Volatility Labs. (2012, September 24). MoVP 3.1 Detecting Malware Hooks in the Windows GUI Subsystem. Retrieved December 12, 2017.
  9. Prekas, G. (2011, July 11). Winhook. Retrieved December 12, 2017.
  10. Satiro, J. (2011, September 14). GetHooks. Retrieved December 12, 2017.
  11. Felici, M. (2006, December 6). Any application-defined hook procedure on my machine?. Retrieved December 12, 2017.
  12. Eye of Ra. (2017, June 27). Windows Keylogger Part 2: Defense against user-land. Retrieved December 12, 2017.