CloseHandle, NtClose

Created the Monday 18 March 2019. Updated 2 months ago.

When a process is debugged, calling NtClose or CloseHandle with an invalid handle will generate a STATUS_INVALID_HANDLE exception.

The exception can be cached by an exception handler. If the control is passed to the exception handler, it indicates that a debugger is present.

Technique Identifiers

U0114 B0001.003

Technique Tags

closehandle ntclose

Featured Windows API's

Below, you will find a list of the most commonly used Windows API's that are currently utilized by malware authors for current evasion technique. This list is meant to provide an overview of the API's that are commonly used for this purpose. If there are any API's that you feel should be included on this list, please do not hesitate to contact us. We will be happy to update the list and provide any additional information or documentation that may be helpful.

CloseHandle

Code Snippets

Description

Original source code is available here: https://anti-debug.checkpoint.com/techniques/object-handles.html#closehandle

bool Check()
{
    __try
    {
        CloseHandle((HANDLE)0xDEADBEEF);
        return false;
    }
    __except (EXCEPTION_INVALID_HANDLE == GetExceptionCode()
                ? EXCEPTION_EXECUTE_HANDLER 
                : EXCEPTION_CONTINUE_SEARCH)
    {
        return true;
    }
}

Detection Rules

                                    rule Detect_CloseHandle: AntiDebug {
    meta: 
        description = "Detect CloseHandle as anti-debug"
        author = "Unprotect"
        comment = "Experimental rule"
    strings:
        $1 = "NtClose" fullword ascii
        $2 = "CloseHandle" fullword ascii
    condition:   
       uint16(0) == 0x5A4D and filesize < 1000KB and any of them
}

                                    rule:
  meta:
    name: check for protected handle exception
    namespace: anti-analysis/anti-debugging/debugger-detection
    author: michael.hunhoff@fireeye.com
    scope: function
    mbc:
      - Anti-Behavioral Analysis::Debugger Detection::SetHandleInformation [B0001.024]
    references:
      - https://github.com/LordNoteworthy/al-khaser/blob/master/al-khaser/AntiDebug/SetHandleInformation_API.cpp
    examples:
      - al-khaser_x86.exe_:0x430D20
  features:
    - and:
      - basic block:
        - and:
          - count(number(2)): 2 or more
          - api: SetHandleInformation
      - api: CloseHandle

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.