FancyBear looks for and executes DLLs in its current directory. Therefore, we can potentially hijack a DLL to execute our own code and control and terminate the malware. The exploit DLL will check if the current directory is "C:\Windows\System32" and if not we grab our process ID and terminate. We do not need to rely on hash signatures or third-party products as the malware's own flaw will do the work for us. Endpoint protection systems and or antivirus can potentially be killed prior to executing malware, but this method cannot as there's nothing to kill the DLL that just lives on disk waiting. From a defensive perspective you can add the DLLs to a specific network share containing important data as a layered approach. All basic tests were conducted successfully in a virtual machine environment.
6c9b981fb52c57e5101af2cf1b3b81f816bca03e29ff6f1e4765d923fb513d91Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2022
Original source: https://malvuln.com/advisory/d6751b148461e0f863548be84020b879.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: APT28 FancyBear
Vulnerability: Code Execution
Description: FancyBear looks for and executes DLLs in its current directory. Therefore, we can potentially hijack a vuln DLL execute our own code, control and terminate the malware. The exploit dll will check if the current directory is "C:\Windows\System32", if not we grab our process ID and terminate. We do not need to rely on hash signature or third-party product, the malwares own flaw will do the work for us. Endpoint protection systems and or antivirus can potentially be killed prior to executing malware, but this method cannot as theres nothing to kill the DLL just lives on disk waiting. From defensive perspective you can add the DLLs to a specific network share containing important data as a layered approach. All basic tests were conducted successfully in a virtual machine environment.
Family: FancyBear
Type: PE32
MD5: d6751b148461e0f863548be84020b879
Vuln ID: MVID-2022-0594
Disclosure: 05/09/2022
Exploit/PoC:
Video Poc URL: https://www.youtube.com/watch?v=8v2bqRX2AEU
Exploit/PoC:
1) Compile the following C code as "winhttp.dll"
2) Place the DLL in same directory as the malware
3) Optional - Hide it: attrib +s +h "winhttp.dll"
4) Run FancyBear
#include "windows.h"
//By malvuln
//Purpose: Exploit FancyBear
//MD5: d6751b148461e0f863548be84020b879
/** DISCLAIMER:
Author is NOT responsible for any damages whatsoever by using this software or improper malware
handling. By using this code you assume and accept all risk implied or otherwise.
**/
//gcc -c winhttp.c -m32
//gcc -shared -o winhttp.dll winhttp.o -m32
BOOL APIENTRY DllMain(HINSTANCE hInst, DWORD reason, LPVOID reserved){
switch (reason) {
case DLL_PROCESS_ATTACH:
MessageBox(NULL, "Code Exec", "by malvuln", MB_OK);
TCHAR buf[MAX_PATH];
GetCurrentDirectory(MAX_PATH, TEXT(buf));
int rc = strcmp("C:\\Windows\\System32", TEXT(buf));
if(rc != 0){
HANDLE handle = OpenProcess(PROCESS_TERMINATE, FALSE, getpid());
if (NULL != handle) {
TerminateProcess(handle, 0);
CloseHandle(handle);
}
}
break;
}
return TRUE;
}
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