Conti ransomware looks for and executes DLLs in its current directory. Therefore, we can potentially hijack a DLL to execute our own code to control and terminate the malware pre-encryption. 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 products, the malware vulnerability 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 is 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.
9cc7ba098e7d73f1ba5a406536afb6daff209000bfc578d3f4921cd931a7e23fDiscovery / credits: Malvuln - malvuln.com (c) 2022
Original source: https://malvuln.com/advisory/3c55ee6753408bff2e3e6a392ed9f2a0.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: Ransom.Conti
Vulnerability: Code Execution
Description: Conti 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 pre-encryption. 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 malware 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: Conti
Type: PE32
MD5: 3c55ee6753408bff2e3e6a392ed9f2a0
SHA256: 0b0b902af452e1c949a609a3b29a9de21dac639846c77427de06e6e63c1fe904
Vuln ID: MVID-2022-0580
Disclosure: 05/03/2022
Video Poc URL: https://www.youtube.com/watch?v=H8TDDklcrPo
Exploit/PoC:
1) Compile the following C code as "netapi32.dll"
2) Place the DLL in same directory as the ransomware
3) Optional - Hide it: attrib +s +h "netapi32.dll"
4) Run the malware
#include "windows.h"
#include "stdio.h"
//By malvuln
//Purpose: Code Execution
//Target: Ransom.Conti
//MD5: 3c55ee6753408bff2e3e6a392ed9f2a0
/** 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 netapi32.c -m32
//gcc -shared -o netapi32.dll netapi32.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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