BKDR_TDSS.SMEO3

July 17, 2013
 Analysis by: kathleenno
 ALIASES:

Backdoor.Tidserv (Symantec); Trojan:Win32/Alureon.DX (Microsoft); Trojan-Downloader.Win32.CodecPack.asag (Kaspersky); Generic Dropper.va.gen.p (Mcafee); Mal/FakeAV-LB (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

It may connect to certain servers where it receives tasks from a remote malicious user. To hide its component files, it writes certain files at the end of the hard disk.

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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

132,608 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 May 2011

Payload:

Hides files and processes, Compromises system security

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 copies of itself into the affected system:

  • %User Temp%\{random}.tmp
  • %User Temp%\setup{random}.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 and 7.)

Other System Modifications

This backdoor deletes the following files:

  • %System%\drivers\etc\hosts

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It adds the following registry entries:

HKEY_USERS\.DEFAULT\Software\
Microsoft\Internet Explorer\Main\
featurecontrol\FEATURE_BROWSER_EMULATION
{executable name} = "{hex value}"

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings
maxhttpredirects = "{hex value}"

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings
enablehttp1_1 = "1"

It modifies the following registry entries:

HKEY_USERS\.DEFAULT\Software\
Microsoft\Internet Explorer\International
acceptlanguage = "{local}"

(Note: The default value data of the said registry entry is {user-defined}.)

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings\zones\3
CurrentLevel = "0"

(Note: The default value data of the said registry entry is {user-defined}.)

HKEY_USERS\.DEFAULT\Software\
Microsoft\Windows\CurrentVersion\
Internet Settings\zones\3
1601 = "0"

(Note: The default value data of the said registry entry is 1.)

Other Details

This backdoor deletes itself after execution.

NOTES:

It may connect to the following servers where it receives tasks from a remote malicious user:

  • https://{BLOCKED}reyk.com/
  • https://{BLOCKED}ewk.com/
  • https://{BLOCKED}haa.com/
  • https://{BLOCKED}nona.com/
  • https://{BLOCKED}ay2k.com/
  • http://{BLOCKED}yawr.com/
  • http://{BLOCKED}wayr.com/
  • http://{BLOCKED}ut0.com/
  • http://{BLOCKED}o0.com/
  • http://{BLOCKED}uke.com/
  • http://{BLOCKED}i813ck.com/

To hide its component files, it writes the following files at the end of the hard disk:

  • \\?\globalroot\{random folder}\bckfg.tmp
  • \\?\globalroot\{random folder}\cfg.ini
  • \\?\globalroot\{random folder}\cmd.dll - detected as Mal_TDSS-16
  • \\?\globalroot\{random folder}\cmd64.dll - detected as BKDR_TDSS.KARU
  • \\?\globalroot\{random folder}\drv32 - detected as RTKT_TDSS.KARUD
  • \\?\globalroot\{random folder}\drv64 - detected as RTKT_TDSS.KARUD
  • \\?\globalroot\{random folder}\ldr16
  • \\?\globalroot\{random folder}\ldr32 - detected as TROJ_TDSS.KARUL
  • \\?\globalroot\{random folder}\ldr64 - detected as TROJ_TDSS.KARUL
  • \\?\globalroot\{random folder}\mbr

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.113.00

FIRST VSAPI PATTERN DATE:

22 Apr 2011

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

Remove the malware/grayware file dropped/downloaded by BKDR_TDSS.SMEO3

Step 3

Restore your system's Master Boot Record (MBR)

To restore your system's Master Boot Record (MBR):

• On Windows 2000, XP, and Server 2003:

  1. Insert your Windows Installation CD into your CD drive then restart your computer.
  2. When prompted, press any key to boot from the CD.
  3. On the Main Menu, type r to enter the Recovery Console.
    (Note for Windows 2000: After pressing r, type c to choose the Recovery Console on the repair options screen.)
  4. Type the number that corresponds to the drive and folder that contains Windows (usually C:\WINDOWS) and press Enter.
  5. Type your Administrator password and press Enter.
  6. In the input box, type the following then press Enter:
    fixmbr {affected drive}
  7. Type exit and press Enter to restart the system normally.

• On Windows Vista and 7:

  1. Insert your Windows Installation DVD into the DVD drive, then press the restart button on your computer.
  2. When prompted, press any key to boot from the DVD.
  3. Depending on your Windows Installation DVD, you might be required to choose the installation language. On the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Repair your computer.
  4. Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
  5. If the Startup Repair window appears, click Cancel, Yes, then Finish.
  6. In the System Recovery Options menu, click Command Prompt.
  7. In the Command Prompt window, type the following then press Enter:
    BootRec.exe /fixmbr
  8. Type exit and press Enter to close the Command Prompt window.
  9. Click Restart to restart your computer normally.

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_USERS\.DEFAULT\Software\Microsoft\Internet Explorer\Main\featurecontrol\FEATURE_BROWSER_EMULATION
    • {executable name} = "{hex value}"
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • maxhttpredirects = "{hex value}"
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • enablehttp1_1 = "1"

Step 5

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_USERS\.DEFAULT\Software\Microsoft\Internet Explorer\International
    • From: acceptlanguage = "{local}"
      To: acceptlanguage = "{user-defined}"
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\zones\3
    • From: CurrentLevel = "0"
      To: CurrentLevel = "{user-defined}"
  • In HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\zones\3
    • From: 1601 = "0"
      To: 1601 = "1"

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_TDSS.SMEO3. 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 7

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%\drivers\etc\hosts


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