Analysis by: Christopher Daniel So
ALIASES:

Trojan:Win32/Dynamer!dtc (Microsoft), Backdoor.Win32.Popwin.dab (Kaspersky), Backdoor.Win32.Popwin (Ikarus)

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This Trojan may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 167,941 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 29 Dec 2010

Arrival Details

This Trojan may be dropped by other malware.

Installation

This Trojan drops the following files:

  • %User Profile%\Application Data\fs.mp3
  • %System%\s3s4312.dat
  • %System%\Windows.dat - detected as TROJ_DYNAMER.SZP

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Keyboard Layouts\E0200804

It adds the following registry entries:

HKEY_CURRENT_USER\Keyboard Layout\Preload
2 = "E0200804"

HKEY_CURRENT_USER\Keyboard Layout\Preload
3 = "00000409"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Keyboard Layouts\E0200804
Ime File = "WINDOWS.DAT"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Keyboard Layouts\E0200804
Layout Text = "Windows±ê×¼ÊäÈë·¨"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Control\Keyboard Layouts\E0200804
Layout File = "kbdus.dll"

It modifies the following registry entries:

HKEY_CURRENT_USER\Keyboard Layout\Preload
1 = "E0200804"

(Note: The default value data of the said registry entry is "00000409".)

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.744.05
VSAPI PATTERN Date: 03 Jan 2011
VSAPI PATTERN Date: 1/3/2011 12:00:00 AM

Step 1

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

Step 2

Remove malware files dropped/downloaded by TROJ_DYNAMER.CDS

    TROJ_DYNAMER.SZP

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\Control\Keyboard Layouts
    • E0200804

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_CURRENT_USER\Keyboard Layout\Preload
    • 2=E0200804
  • In HKEY_CURRENT_USER\Keyboard Layout\Preload
    • 3=00000409

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_CURRENT_USER\Keyboard Layout\Preload
    • From: 1=E0200804
      To: 1=00000409

Step 6

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. %User Profile%\Application Data\fs.mp3
%System%\s3s4312.dat

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_DYNAMER.CDS 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.


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