ALIASES:

Backdoor.Win32.Bifrose.efsk (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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: 3,346,573 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 May 2013

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 creates the following folders:

  • \?\C:\DOCUME~1\Wilbert\LOCALS~1\Temp\ckz_P67B
  • \?\C:\DOCUME~1\Wilbert\LOCALS~1\Temp\ckz_P67B\Registration_Win
  • %User Temp%\is-1M54U.tmp
  • %User Temp%\is-T78C5.tmp
  • %User Temp%\is-T78C5.tmp\_isetup
  • %System Root%\CSCClientRegistration

(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 and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
CSCProxyExecuter = "%System Root%\CSCClientRegistration\CSCProxyExecuter.exe"

It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Test

Other System Modifications

This backdoor deletes the following files:

  • %System Root%\CSCClientRegistration\Application.log

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\CSCClient

HKEY_LOCAL_MACHINE\Software\CSCClient\
Registration

HKEY_LOCAL_MACHINE\Software\CSCClient\
Registration\Parameters

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\
Registration\Parameters
Application = "%System Root%\CSCClientRegistration\CSCClientRegistration.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\
Registration\Parameters
Ver = "1.0.7"

HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\
Registration\Parameters
UnInstallPath = "%System Root%\CSCClientRegistration\unins000.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
Inno Setup: Setup Version = "5.1.4"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
Inno Setup: App Path = "%System Root%\CSCClientRegistration"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
InstallLocation = "%System Root%\CSCClientRegistration"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
Inno Setup: Icon Group = "CSCClientRegistration"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
Inno Setup: User = "Wilbert"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
DisplayName = "CSC Client Registration"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
DisplayIcon = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
UninstallString = "%System Root%\CSCClientRegistration\unins000.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
QuietUninstallString = "%System Root%\CSCClientRegistration\unins000.exe /SILENT"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
Publisher = "CSC ONLINE MONITORING"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
NoModify = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1
NoRepair = "1"

It deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
CSC Client Registration_is1

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Test

Dropping Routine

This backdoor drops the following files:

  • Registration_Win\setup.exe
  • %User Temp%\is-1M54U.tmp\is-EF6RU.tmp
  • %User Temp%\is-T78C5.tmp\_isetup\_shfoldr.dll
  • %User Temp%\is-T78C5.tmp\Prerequisite.exe
  • %System Root%\CSCClientRegistration\unins000.dat
  • %System Root%\CSCClientRegistration\is-PV6P0.tmp
  • %System Root%\CSCClientRegistration\is-76UIC.tmp
  • %System Root%\CSCClientRegistration\is-9USFK.tmp
  • %System Root%\CSCClientRegistration\is-3ISP1.tmp
  • %System Root%\CSCClientRegistration\is-L3RSC.tmp
  • %System Root%\CSCClientRegistration\is-PLJIB.tmp
  • %System Root%\CSCClientRegistration\is-6BUQC.tmp
  • %System Root%\CSCClientRegistration\is-6I75O.tmp
  • %System Root%\CSCClientRegistration\is-ID9ET.tmp
  • %System Root%\CSCClientRegistration\is-GNNE0.tmp
  • %System Root%\CSCClientRegistration\is-VKHVK.tmp
  • %System Root%\CSCClientRegistration\is-DE671.tmp
  • %System Root%\CSCClientRegistration\is-LL0OB.tmp
  • %System Root%\CSCClientRegistration\is-KCOC3.tmp
  • %System Root%\CSCClientRegistration\is-UKL15.tmp
  • %System Root%\CSCClientRegistration\is-1CD5L.tmp
  • %System Root%\CSCClientRegistration\is-KNQ4D.tmp
  • %System Root%\CSCClientRegistration\is-I887D.tmp
  • %System Root%\CSCClientRegistration\is-00P4M.tmp
  • %System Root%\CSCClientRegistration\is-4H9UB.tmp
  • %System Root%\CSCClientRegistration\is-H0J2R.tmp
  • %System Root%\CSCClientRegistration\is-Q8IEL.tmp
  • %System Root%\CSCClientRegistration\is-PNFJV.tmp
  • %System Root%\CSCClientRegistration\is-RNB1R.tmp
  • %System Root%\CSCClientRegistration\is-DSC7E.tmp
  • %System Root%\CSCClientRegistration\is-DQI4K.tmp
  • %System Root%\CSCClientRegistration\is-SJNSQ.tmp
  • %System Root%\CSCClientRegistration\is-4B5KU.tmp
  • %System Root%\CSCClientRegistration\is-4779T.tmp
  • %System Root%\CSCClientRegistration\is-UQ801.tmp
  • %System Root%\CSCClientRegistration\is-5GDGS.tmp
  • %System Root%\CSCClientRegistration\is-NSRGC.tmp
  • %System Root%\CSCClientRegistration\is-Q2561.tmp
  • %System Root%\CSCClientRegistration\is-40GBL.tmp
  • %System Root%\CSCClientRegistration\is-PCM60.tmp
  • %System%\MSWINSCK.OCX

(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 and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.300

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ 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\SYSTEM\CurrentControlSet\Services
    • Test
  • In HKEY_LOCAL_MACHINE\Software
    • CSCClient
  • In HKEY_LOCAL_MACHINE\Software\CSCClient
    • Registration
  • In HKEY_LOCAL_MACHINE\Software\CSCClient\Registration
    • Parameters
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall
    • CSC Client Registration_is1

Step 4

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • CSCProxyExecuter = "%System Root%\CSCClientRegistration\CSCProxyExecuter.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\Registration\Parameters
    • Application = "%System Root%\CSCClientRegistration\CSCClientRegistration.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\Registration\Parameters
    • Ver = "1.0.7"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\CSCClient\Registration\Parameters
    • UnInstallPath = "%System Root%\CSCClientRegistration\unins000.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • Inno Setup: Setup Version = "5.1.4"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • Inno Setup: App Path = "%System Root%\CSCClientRegistration"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • InstallLocation = "%System Root%\CSCClientRegistration"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • Inno Setup: Icon Group = "CSCClientRegistration"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • Inno Setup: User = "Wilbert"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • DisplayName = "CSC Client Registration"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • DisplayIcon = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • UninstallString = "%System Root%\CSCClientRegistration\unins000.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • QuietUninstallString = "%System Root%\CSCClientRegistration\unins000.exe /SILENT"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • Publisher = "CSC ONLINE MONITORING"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • NoModify = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\CSC Client Registration_is1
    • NoRepair = "1"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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.
  • Registration_Win\setup.exe
  • %User Temp%\is-1M54U.tmp\is-EF6RU.tmp
  • %User Temp%\is-T78C5.tmp\_isetup\_shfoldr.dll
  • %User Temp%\is-T78C5.tmp\Prerequisite.exe
  • %System Root%\CSCClientRegistration\unins000.dat
  • %System Root%\CSCClientRegistration\is-PV6P0.tmp
  • %System Root%\CSCClientRegistration\is-76UIC.tmp
  • %System Root%\CSCClientRegistration\is-9USFK.tmp
  • %System Root%\CSCClientRegistration\is-3ISP1.tmp
  • %System Root%\CSCClientRegistration\is-L3RSC.tmp
  • %System Root%\CSCClientRegistration\is-PLJIB.tmp
  • %System Root%\CSCClientRegistration\is-6BUQC.tmp
  • %System Root%\CSCClientRegistration\is-6I75O.tmp
  • %System Root%\CSCClientRegistration\is-ID9ET.tmp
  • %System Root%\CSCClientRegistration\is-GNNE0.tmp
  • %System Root%\CSCClientRegistration\is-VKHVK.tmp
  • %System Root%\CSCClientRegistration\is-DE671.tmp
  • %System Root%\CSCClientRegistration\is-LL0OB.tmp
  • %System Root%\CSCClientRegistration\is-KCOC3.tmp
  • %System Root%\CSCClientRegistration\is-UKL15.tmp
  • %System Root%\CSCClientRegistration\is-1CD5L.tmp
  • %System Root%\CSCClientRegistration\is-KNQ4D.tmp
  • %System Root%\CSCClientRegistration\is-I887D.tmp
  • %System Root%\CSCClientRegistration\is-00P4M.tmp
  • %System Root%\CSCClientRegistration\is-4H9UB.tmp
  • %System Root%\CSCClientRegistration\is-H0J2R.tmp
  • %System Root%\CSCClientRegistration\is-Q8IEL.tmp
  • %System Root%\CSCClientRegistration\is-PNFJV.tmp
  • %System Root%\CSCClientRegistration\is-RNB1R.tmp
  • %System Root%\CSCClientRegistration\is-DSC7E.tmp
  • %System Root%\CSCClientRegistration\is-DQI4K.tmp
  • %System Root%\CSCClientRegistration\is-SJNSQ.tmp
  • %System Root%\CSCClientRegistration\is-4B5KU.tmp
  • %System Root%\CSCClientRegistration\is-4779T.tmp
  • %System Root%\CSCClientRegistration\is-UQ801.tmp
  • %System Root%\CSCClientRegistration\is-5GDGS.tmp
  • %System Root%\CSCClientRegistration\is-NSRGC.tmp
  • %System Root%\CSCClientRegistration\is-Q2561.tmp
  • %System Root%\CSCClientRegistration\is-40GBL.tmp
  • %System Root%\CSCClientRegistration\is-PCM60.tmp
  • %System%\MSWINSCK.OCX

Step 6

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • \?\C:\DOCUME~1\Wilbert\LOCALS~1\Temp\ckz_P67B
  • \?\C:\DOCUME~1\Wilbert\LOCALS~1\Temp\ckz_P67B\Registration_Win
  • %User Temp%\is-1M54U.tmp
  • %User Temp%\is-T78C5.tmp
  • %User Temp%\is-T78C5.tmp\_isetup
  • %System Root%\CSCClientRegistration

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_BIFROSE.YIR. 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 this Knowledge Base page for more information.

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %System Root%\CSCClientRegistration\Application.log

Step 9

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Uninstall
    • CSC Client Registration_is1
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services
    • Test


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