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TROJ_SCAR.AAA

October 12, 2012
 ALIASES:

Trojan:Win32/Sisproc (Microsoft); BackDoor-CEP!bdt (McAfee); PAK:UPX, ARC:BatToExe, [7.exe]:Backdoor.Win32.Bifrose.efsi, [7.exe]:Backdoor.Win32.Bifrose.efsi (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan.Generic.7050643 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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:

73,728 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

29 Mar 2012

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 creates the following folders:

  • %User Temp%\1.tmp

(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.)

Autostart Technique

This Trojan registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\1.tmp

(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.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Description\
Microsoft\Rpc\UuidTemporaryData

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0\
FLAGS

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0\
0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0\
0\win32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0\
HELPDIR

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}\ProxyStubClsid

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}\ProxyStubClsid32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}\TypeLib

HKEY_CLASSES_ROOT\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}\InprocServer32

HKEY_CLASSES_ROOT\Wmbrowser.Wmbrowsers

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Description\
Microsoft\Rpc\UuidTemporaryData
NetworkAddress = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Description\
Microsoft\Rpc\UuidTemporaryData
NetworkAddressLocal = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLUA = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}\TypeLib
Version = "1.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
ProgID = "Wmbrowser.Wmbrowsers"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}\InprocServer32
ThreadingModel = "Apartment"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
TypeLib = "{8D8BB208-8253-4783-9363-B8B3A8125383}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
VERSION = "1.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Wmbrowser.Wmbrowsers
Clsid = "{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
ProxyStubClsid = "{00020424-0000-0000-C000-000000000046}"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
ProxyStubClsid32 = "{00020424-0000-0000-C000-000000000046}"

Dropping Routine

This Trojan drops the following files:

  • 7.exe
  • %Windows%\Wmbrowser.dll
  • %User Temp%\readfloopxm23a.tmp

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.. %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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Close all opened browser windows

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\Software\Description\Microsoft\Rpc
    • UuidTemporaryData
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • Browser Helper Objects
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
    • {8D8BB208-8253-4783-9363-B8B3A8125383}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}
    • 1.0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0
    • FLAGS
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0
    • 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0\0
    • win32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{8D8BB208-8253-4783-9363-B8B3A8125383}\1.0
    • HELPDIR
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
    • {BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
    • ProxyStubClsid
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
    • ProxyStubClsid32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
    • TypeLib
  • In HKEY_CLASSES_ROOT\CLSID
    • {EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
    • InprocServer32
  • In HKEY_CLASSES_ROOT
    • Wmbrowser.Wmbrowsers

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\Description\Microsoft\Rpc\UuidTemporaryData
    • NetworkAddress = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Description\Microsoft\Rpc\UuidTemporaryData
    • NetworkAddressLocal = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • EnableLUA = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}\TypeLib
    • Version = "1.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
    • ProgID = "Wmbrowser.Wmbrowsers"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}\InprocServer32
    • ThreadingModel = "Apartment"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
    • TypeLib = "{8D8BB208-8253-4783-9363-B8B3A8125383}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}
    • VERSION = "1.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Wmbrowser.Wmbrowsers
    • Clsid = "{EF949D99-C1DD-4D53-AA7E-C1286EFB93E1}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
    • ProxyStubClsid = "{00020424-0000-0000-C000-000000000046}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{BA4CB01C-0E8D-4EB3-809E-4ECF07622105}
    • ProxyStubClsid32 = "{00020424-0000-0000-C000-000000000046}"

Step 5

Search and delete these files

[ Learn More ]
There may be some component 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.
  • 7.exe
  • %Windows%\Wmbrowser.dll
  • %User Temp%\readfloopxm23a.tmp

Step 6

Search and delete this folder

[ 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.
  • %User Temp%\1.tmp

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_SCAR.AAA. 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.

  • %User Temp%\1.tmp


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