ALIASES:

Trojan:Win32/Alureon.CT (Microsoft); Backdoor.Tidserv!gen7 (Symantec); DNSChanger.as (McAfee); Trojan-Dropper.Win32.TDSS.fzx (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 96,768 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 20 Oct 2010

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 copies of itself into the affected system:

  • %User Temp%\{random number}.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.)

Other System Modifications

This Trojan 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 Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}l01.com/
  • http://{BLOCKED}3ja90a.com/
  • http://{BLOCKED}10h.com/
  • http://{BLOCKED}yhks66.com/
  • http://{BLOCKED}ga64aa17.com/
  • http://{BLOCKED}e3oo8as0.com/
  • http://{BLOCKED}1s6cx0.com/
  • http://{BLOCKED}gh716zzl.com/
  • http://{BLOCKED}cv1.com/
  • http://{BLOCKED}cv1.com/
  • https://{BLOCKED}4cx00.cc/
  • https://{BLOCKED}.226.67/
  • https://{BLOCKED}b0.com/
  • https://{BLOCKED}b0.com/
  • https://{BLOCKED}3.com/
  • https://{BLOCKED}dden.in/
  • https://{BLOCKED}fda88.com/

It deletes itself after execution.

  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

Restore your system’s Master Boot Record (MBR)

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

  1. Insert your Windows Installation CD into your CD-ROM drive or the USB flash drive then restart your computer.
  2. Press the restart button of your computer.
  3. When prompted, press any key to boot from the CD.
  4. When prompted on the Main Menu, type r to enter the Recovery Console.
    (For Windows 2000 users: After pressing r, type c to choose the Recovery Console on the repair options screen.)
  5. When prompted, type your administrator password to log in.
  6. Once logged in, type the drive that contains Windows in the command prompt that appears, and then press Enter.
  7. Type the following then press Enter:
    fixmbr {affected drive}
    (Note: The affected drive is the bootable drive that this malware/grayware has affected. If no device is specified, the MBR will be written in the primary boot drive.)
  8. Type exit to restart the system.

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_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 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_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 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_TDSS.BLC. 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.

NOTES:

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