Backdoor.Win64.REMCOS.AA

November 04, 2020
 Analysis by: Clive Fuentebella
 ALIASES:

Win32/TrojanDownloader.Delf.CZQ trojan (NOD32)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

646,144 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Nov 2020

Arrival Details

This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Backdoor drops the following files:

  • %User Temp%\IXP000.TMP\TMP4351$.TMP
  • %User Temp%\IXP000.TMP\DOCUMENT2.EXE
  • %AppDataLocal%\Microsoft\Windows\Inczdrv.exe
  • %AppDataLocal%\zcnI.url
  • %Application Data%\microsoftwndddows98\logs.dat

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • %User Temp%\IXP000.TMP\DOCUMENT2.EXE
  • %Program Files%\internet explorer\ieinstal.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
wextract_cleanup0 = rundll32.exe %System%\advpack.dll,DelNodeRunDLL32 "%User Temp%\IXP000.TMP\"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Incz = %AppDataLocal%\zcnI.url

HKEY_CURRENT_USER\Software\microsoftwndddows98-Q8G3TQ
exepath = T\xd1

HKEY_CURRENT_USER\Software\microsoftwndddows98-Q8G3TQ
licence = 23121EFCD91EE2385BE3F8ABABB805B3

Other Details

This Backdoor connects to the following possibly malicious URL:

  • style.{BLOCKED}sps.co.id