Analysis by: Arvin Roi Macaraeg

ALIASES:

Trojan:Win32/Ramnit(MICROSOFT), Trojan.Win32.Zenpak.bdt(KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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: 239,104 bytes
File Type: , EXE
Memory Resident: Yes
Initial Samples Received Date: 27 Sep 2018

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %AppDataLocal%\{random filename}.log
  • %Program Data%\{random filename}.log
  • %AppDataLocalLow%\com.{User Name}.sdb
  • %AppDataLocalLow%\cmd.{User Name}.bat

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.. %AppDataLocalLow% is the LocalLow Application Data folder, which is usually C:\Users\{user name}\AppData\LocalLow on Windows Vista, 7, and 8.)

It drops the following copies of itself into the affected system:

  • %User Temp%\{random filename}.exe
  • %User Startup%\{random filename}.exe
  • %AppDataLocal%\{Random Folder name}\{random filename}.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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows XP, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista, 7, and 8.)

It adds the following processes:

  • svchost.exe
  • "%System%\sdbinst.exe" /q "%AppDataLocalLow%\com.{User Name}.sdb"
  • cmd /c %AppDataLocalLow%\cmd.{User Name}.bat

(Note: %AppDataLocalLow% is the LocalLow Application Data folder, which is usually C:\Users\{user name}\AppData\LocalLow on Windows Vista, 7, and 8.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random filename} = "%User Temp%\{random filename}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random filename} = "%AppDataLocal%\{Random Folder name}\{random filename}.exe"

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusOverride = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusDisableNotify = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallDisableNotify = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallOverride = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UpdatesDisableNotify = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UacDisableNotify = "1"

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.626.04
FIRST VSAPI PATTERN DATE: 14 Nov 2018
VSAPI OPR PATTERN File: 14.627.00
VSAPI OPR PATTERN Date: 15 Nov 2018

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

 
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random filename} = "%AppDataLocal%\{Random Folder name}\{random filename}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random filename} = "%User Temp%\{random filename}.exe"

Step 4

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: AntiVirusOverride = "1"
      To: AntiVirusOverride = {Default Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: AntiVirusDisableNotify = "1"
      To: AntiVirusDisableNotify = {Default Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: FirewallDisableNotify = "1"
      To: FirewallDisableNotify = {Default Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: FirewallOverride = "1"
      To: FirewallOverride = {Default Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: UpdatesDisableNotify = "1"
      To: UpdatesDisableNotify = {Default Value}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Security Center
    • From: UacDisableNotify = "1"
      To: UacDisableNotify = {Default Value}

Step 5

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\{random filename}.exe
  • %User Startup%\{random filename}.exe
  • %AppDataLocal%\{Random Folder name}\{random filename}.exe
  • %AppDataLocal%\{random filename}.log
  • %Program Data%\{random filename}.log
  • %AppDataLocalLow%\com.{User Name}.sdb
  • %AppDataLocalLow%\cmd.{User Name}.bat

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.RAMNIT.A. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check the following Trend Micro Support pages for more information:


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