Discovery / credits: Malvuln - (c) 2021  
Original source:  
Threat: Backdoor.Win32.DarkKomet.irv  
Vulnerability: Insecure Permissions  
Description: DarkKomet.irv creates an insecure dir named "Windupdt" under c:\ drive, granting change (C) permissions to authenticated user group. Standard users can rename the malware and reboot to disable it or replace it with their own executable to escalate privileges when a privileged user logs on. DarkKomet also creates auto start registry keys under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon "Userinit" and drops three other files under "AppData\Local\Temp". To successfully rename the malware we have to call Windows "attrib -h" command to unhide the executable or the rename will fail.  
Type: PE32  
MD5: a229acff4e0605ad24eaf3d9c44fdb1b  
Vuln ID: MVID-2021-0105  
Dropped files: winupdate.exe, [TGS]CAPUB V1.11.EXE, [TGS]CAPUB V1.11.DLL, dclogs.sys  
Disclosure: 02/21/2021  
#include "stdio.h"  
#include "windows.h"  
void main(void){  
system("attrib -h C:\\Windupdt\\winupdate.exe");  
puts("Unhiding the malware to rename it...");  
system("RENAME C:\\Windupdt\\winupdate.exe 13");  
printf("[+] Disabled persistence by renaming winupdate.exe to 13 ...\n");  
printf("Restart your computer ...");  
puts("[+] Backdoor.Win32.DarkKomet.irv PWNED!\n");  
puts("[+] MD5: a229acff4e0605ad24eaf3d9c44fdb1b\n");  
puts("[+] By Malvuln\n");  
C:\Windupdt BUILTIN\Administrators:(OI)(CI)(ID)F  
NT AUTHORITY\Authenticated Users:(ID)C  
NT AUTHORITY\Authenticated Users:(OI)(CI)(IO)(ID)C  
C:\>dir \Windupdt  
Volume in drive C has no label.  
Directory of C:\Windupdt  
C:\>dir /a \Windupdt  
Volume in drive C has no label.  
Directory of C:\Windupdt  
06/14/2012 10:58 PM 1,433,088 winupdate.exe  
1 File(s) 1,537,340 bytes  
2 Dir(s) 49,992,314,880 bytes free  
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