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BKDR_SIMDA.TU

October 09, 2012
 ALIASES:

Backdoor:Win32/Simda (Microsoft), Generic BackDoor.acr (McAfeE)

 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 as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

835,085 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

24 Aug 2012

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 files:

  • %User Profile%\Application Data\{random 4}.reg
  • %User Profile%\Application Data\mcp.ico
  • %User Profile%\Application Data\Mozilla\Firefox\Profiles\{random}\searchplugins\search.xml
  • %Desktop%\Computer.lnk
  • %User Temp%\{random 3}.sys
  • %User Temp%\{random 1}.exe
  • %User Temp%\{random number}.tmp
  • %User Temp%\{random 2}.exe

(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.. %Desktop% is the current user's desktop, which is usually C:\Windows\Profiles\{user name}\Desktop on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Desktop on Windows NT, and C:\Documents and Settings\{User Name}\Desktop on Windows 2000, XP, and Server 2003.. %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 drops the following copies of itself into the affected system:

  • %User Profile%\Application Data\ScanDisc.exe
  • %User Profile%\Application Data\{random name}.exe
  • %User Temp%\{Random Number}.tmp

(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.. %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 executes then deletes itself afterward.

Autostart Technique

This backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
{random name} = "%User Profile%\Application Data\{random name}.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
ConsentPromptBehaviorAdmin = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
ConsentPromptBehaviorUser = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnableLUA = "0"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows
update = "shortcut"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Tcpip\Parameters\
Interfaces\{GUID}
NameServer = "8.8.8.8"

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

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.143.99
  • {BLOCKED}.{BLOCKED}.176.187
  • {BLOCKED}.{BLOCKED}.15.124
  • {BLOCKED}.{BLOCKED}.131.121
  • {BLOCKED}.{BLOCKED}.87.103
  • {BLOCKED}.{BLOCKED}.87.147
  • {BLOCKED}.{BLOCKED}.83.112
  • {BLOCKED}.{BLOCKED}.173.222
  • {BLOCKED}.{BLOCKED}.37.21
  • {BLOCKED}.{BLOCKED}.68.97
  • {BLOCKED}.{BLOCKED}.201.1
  • http://update1.{BLOCKED}eanerlrcn.com/?abbr=RTK&action=download&setupType=umx&setupFileName=process_64.exe
  • http://update1.{BLOCKED}string.com/update_c1eec.ex
  • {BLOCKED}t.{pseudorandom}.com
  • {BLOCKED}e.{pseudorandom}.com

NOTES:

It appends the legitimate file %User Profile%\Application Data\Mozilla\Firefox\Profiles\{random}\prefs.js with user_pref(&"browser.search.selectedEngine&"_http://{BLOCKED}la.com/?&uid={number}&q={searchTerms}");.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.346.03

FIRST VSAPI PATTERN DATE:

24 Aug 2012

VSAPI OPR PATTERN File:

9.347.00

VSAPI OPR PATTERN Date:

25 Aug 2012

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

Scan your computer with your Trend Micro product and note files detected as BKDR_SIMDA.TU

Step 3

Restart in Safe Mode

[ Learn More ]

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\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • {random name} = "%User Profile%\Application Data\{random name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • ConsentPromptBehaviorAdmin = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • ConsentPromptBehaviorUser = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
    • EnableLUA = "0"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows
    • update = "shortcut"

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{GUID}
    • From: NameServer = "8.8.8.8"
      To: NameServer = ""

Step 6

Search and delete this file

[ 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\{random 4}.reg
  • %User Profile%\Application Data\mcp.ico
  • %User Profile%\Application Data\Mozilla\Firefox\Profiles\{random}\searchplugins\search.xml
  • %Desktop%\Computer.lnk
  • %User Temp%\{random 3}.sys
  • %User Temp%\{random 1}.exe
  • %User Temp%\{random number}.tmp
  • %User Temp%\{random 2}.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_SIMDA.TU. 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:

Before proceeding to Step 7, do the following steps to remove the strings added by the malware/grayware/spyware in the file %User Profile%\Application Data\Mozilla\Firefox\Profiles\{random}\prefs.js file:

  1. Open the file %User Profile%\Application Data\Mozilla\Firefox\Profiles\{random}\prefs.js using a text editor such as Notepad. Find and delete the following entry:
    user_pref(&"browser.search.selectedEngine&"_http://{BLOCKED}la.com/?&uid={number}&q={searchTerms}");
  2. Save the file then close the text editor.


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