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Debugger Evasion

Adversaries may employ various means to detect and avoid debuggers. Debuggers are typically used by defenders to trace and/or analyze the execution of potential malware payloads.[1]

Debugger evasion may include changing behaviors based on the results of the checks for the presence of artifacts indicative of a debugged environment. Similar to Virtualization/Sandbox Evasion, if the adversary detects a debugger, they may alter their malware to disengage from the victim or conceal the core functions of the implant. They may also search for debugger artifacts before dropping secondary or additional payloads.

Specific checks will vary based on the target and/or adversary, but may involve Native API function calls such as IsDebuggerPresent() and NtQueryInformationProcess(), or manually checking the BeingDebugged flag of the Process Environment Block (PEB). Other checks for debugging artifacts may also seek to enumerate hardware breakpoints, interrupt assembly opcodes, time checks, or measurements if exceptions are raised in the current process (assuming a present debugger would "swallow" or handle the potential error).[2][3][4]

Adversaries may use the information learned from these debugger checks during automated discovery to shape follow-on behaviors. Debuggers can also be evaded by detaching the process or flooding debug logs with meaningless data via messages produced by looping Native API function calls such as OutputDebugStringW().[5][6]

ID: T1622
Sub-techniques:  No sub-techniques
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Tactics: Defense Evasion, Discovery
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Platforms: Linux, Windows, macOS
Contributors: TruKno
Version: 1.0
Created: 01 April 2022
Last Modified: 16 April 2022
Version Permalink

Procedure Examples

ID Name Description
S1087 AsyncRAT

AsyncRAT can use the CheckRemoteDebuggerPresent function to detect the presence of a debugger.[7]
S1070 Black Basta

The Black Basta dropper can check system flags, CPU registers, CPU instructions, process timing, system libraries, and APIs to determine if a debugger is present.[8]
S1039 Bumblebee

Bumblebee can search for tools used in static analysis.[9]
S1111 DarkGate

DarkGate checks the BeingDebugged flag in the PEB structure during execution to identify if the malware is being debugged.[10]
S1066 DarkTortilla

DarkTortilla can detect debuggers by using functions such as DebuggerIsAttached and DebuggerIsLogging. DarkTortilla can also detect profilers by verifying the COR_ENABLE_PROFILING environment variable is present and active.[11]
S0694 DRATzarus

DRATzarus can use IsDebuggerPresent to detect whether a debugger is present on a victim.[12]
S1060 Mafalda

Mafalda can search for debugging tools on a compromised host.[13]
C0022 Operation Dream Job

During Operation Dream Job, Lazarus Group used tools that used the IsDebuggerPresent call to detect debuggers.[12]
S0240 ROKRAT

ROKRAT can check for debugging tools.[14][15][16]
S1018 Saint Bot

Saint Bot has used is_debugger_present as part of its environmental checks.[17]
S0595 ThiefQuest

ThiefQuest uses a function named is_debugging to perform anti-debugging logic. The function invokes sysctl checking the returned value of P_TRACED. ThiefQuest also calls ptrace with the PTRACE_DENY_ATTACH flag to prevent debugging.[5]

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
DS0015 Application Log Application Log Content

Monitor debugger logs for signs of abnormal and potentially malicious activity.
DS0017 Command Command Execution

Monitor executed commands and arguments that may employ various means to detect and avoid debugged environments. Detecting actions related to debugger identification may be difficult depending on the adversary's implementation and monitoring required.
DS0009 Process OS API Execution

Monitor for API calls (such as IsDebuggerPresent()) that may employ various means to detect and avoid debugged environments. Detecting actions related to debugger identification may be difficult depending on the adversary's implementation and monitoring required.
Process Creation

Monitoring for suspicious processes being spawned that gather a variety of system information or perform other forms of Discovery, especially in a short period of time, may aid in detection. Debugger related system checks will likely occur in the first steps of an operation but may also occur throughout as an adversary learns the environment. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as lateral movement, based on the information obtained.

References

  1. ProcessHacker. (2009, October 27). Process Hacker. Retrieved April 11, 2022.
  2. hasherezade. (2021, June 30). Module 3 - Understanding and countering malware's evasion and self-defence. Retrieved April 1, 2022.
  3. Noteworthy. (2019, January 6). Al-Khaser. Retrieved April 1, 2022.
  4. vxunderground. (2021, June 30). VX-API. Retrieved April 1, 2022.
  5. Patrick Wardle. (2020, July 3). OSX.EvilQuest Uncovered part ii: insidious capabilities. Retrieved March 21, 2021.
  6. Check Point Research. (2021, January 4). Stopping Serial Killer: Catching the Next Strike. Retrieved September 7, 2021.
  7. Jornet, A. (2021, December 23). Snip3, an investigation into malware. Retrieved September 19, 2023.
  8. Check Point. (2022, October 20). BLACK BASTA AND THE UNNOTICED DELIVERY. Retrieved March 8, 2023.
  9. Salem, A. (2022, April 27). The chronicles of Bumblebee: The Hook, the Bee, and the Trickbot connection. Retrieved September 2, 2022.
  1. Ernesto Fernández Provecho, Pham Duy Phuc, Ciana Driscoll & Vinoo Thomas. (2023, November 21). The Continued Evolution of the DarkGate Malware-as-a-Service. Retrieved February 9, 2024.
  2. Secureworks Counter Threat Unit Research Team. (2022, August 17). DarkTortilla Malware Analysis. Retrieved November 3, 2022.
  3. ClearSky Research Team. (2020, August 13). Operation 'Dream Job' Widespread North Korean Espionage Campaign. Retrieved December 20, 2021.
  4. SentinelLabs. (2022, September 22). Metador Technical Appendix. Retrieved April 4, 2023.
  5. Mercer, W., Rascagneres, P. (2018, January 16). Korea In The Crosshairs. Retrieved May 21, 2018.
  6. Pantazopoulos, N.. (2018, November 8). RokRat Analysis. Retrieved May 21, 2020.
  7. Jazi, Hossein. (2021, January 6). Retrohunting APT37: North Korean APT used VBA self decode technique to inject RokRat. Retrieved March 22, 2022.
  8. Hasherezade. (2021, April 6). A deep dive into Saint Bot, a new downloader. Retrieved June 9, 2022.