BKDR_SIMDA.SS

 Analysis by: Sabrina Lei Sioting

 ALIASES:

Backdoor:Win32/Simda.gen!A (Microsoft), Backdoor.Trojan (Symantec), Generic BackDoor.acx (McAfee), BDS/Simda.A.43 (Antivir), Backdoor.Simda.A (Bitdefender), W32/Shiz.NCF!tr (Fortinet), Backdoor.Win32.Simda (Ikarus),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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 executes commands from a remote malicious user, effectively compromising the affected system.

It attempts to steal information, such as user names and passwords, used when logging into certain banking or finance-related websites.

It prevents users from visiting antivirus-related websites that contain specific strings.

  TECHNICAL DETAILS

File Size:

227,328 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

29 Aug 2012

Payload:

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:

  • %Windows%\AppPatch\{random}.dat

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

It injects itself into the following processes running in the affected system's memory:

  • winlogon.exe
  • explorer.exe

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • B0B2D5C3a

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
b0b2d6e3 = "%Windows%\AppPatch\{random}.dat"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,%Windows%\AppPatch\{random}.dat,"

(Note: The default value data of the said registry entry is "%System%\userinit.exe,".)

Other System Modifications

This backdoor creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:Windows Explorer"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Disable operating system by modifying or deleting system files
  • Activate/deactivate itself
  • Inject scripts to a visited webpage
  • Disable the infected system by deleting critical registry keys
  • Download and execute arbitrary files
  • Download updated configuration file
  • Upload files
  • Run or terminate applications
  • Delete files
  • Modify system settings
  • Steal certificates

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.com/login.php

Dropping Routine

This backdoor drops the following file(s), which it uses for its keylogging routine:

  • %User Profile%\Application Data\{random}
  • %User Profile%\Application Data\{random1}

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Information Theft

This backdoor attempts to steal information from the following banks and/or other financial institutions:

  • IBANK
  • ebank.laiki.com
  • w.qiwi.ru
  • login.yota.ru

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • www.bing.com
  • www.microsoft.com

It closes application windows that contain the following strings in the title bar:

  • ____AVP.Root

It prevents users from visiting antivirus-related websites that contain the following strings:

  • avast.com
  • kaspersky
  • drweb
  • eset.com
  • antivir
  • avira
  • virustotal
  • virusinfo
  • z-oleg.com
  • trendsecure
  • anti-malware
  • .comodo.com

NOTES:

It terminates itself if the system's username is any of the following:

  • SANDBOX
  • MALNETVM
  • VIRUSCLONE

It also terminates itself if the following folders are present in the system:

  • \sand-box\
  • \cwsandbox\
  • \sandbox\

It terminates AV related processes by:

For CA HIPS, it sends control code to the product’s driver:

  • \\.\KmxAgent

For AVG, it renames the following files:

  • %Program Files%\AVG\AVG9\dfncfg.dat to %Program Files%\AVG\AVG9\dfmcfg.dat%

For Prevx, it modifies the following files:

  • %System Root%\Documents and Settings\All Users\Application Data\PrevxCSI\csidb.csi

It changes to Windows Defender status by modifying the following files:

  • %Program Files%\Windows Defender\MpClient.dll

It attempts to log on to the system as Administrator (if not yet Administrator) by using the following passwords:

  • -help
  • stone
  • server
  • idontknow
  • administrator
  • admin
  • 666666
  • 12345678
  • soccer
  • abc123
  • password1
  • football1
  • fuckyou
  • monkey
  • iloveyou1
  • superman1
  • slipknot1
  • jordan23
  • princess1
  • liverpool1
  • monkey1
  • baseball1
  • 123abc
  • qwerty1
  • blink182
  • myspace1
  • user111
  • 098765
  • qweryuiopas
  • qwert
  • qwerty
  • asdfg
  • chort
  • xakep
  • 111111
  • 12345
  • password
  • 123456

When this malware is already injected in winlogon.exe or explorer.exe, it tries to inject itself on the folllowing processes:

  • iexplore.exe
  • opera.exe
  • java.exe
  • javaw.exe
  • explorer.exe
  • isclient.exe
  • intpro.exe
  • ipc_full.exe
  • mnp.exe
  • cbsmain.dll
  • firefox.exe
  • clmain.exe
  • core.exe
  • maxthon.exe
  • avant.exe
  • safari.exe
  • svchost.exe
  • chrome.exe
  • notepad.exe
  • rundll32.exe
  • netscape.exe
  • tbb-firefox.exe
  • frd.exe

It uses the following referrer when connecting to its C&C server:

  • http://www.google.com

  SOLUTION

Minimum Scan Engine:

9.300

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

Identify and delete files detected as BKDR_SIMDA.SS using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe,%Windows%\AppPatch\{random}.dat,"
      To: Userinit = "%System%\userinit.exe,"

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\Microsoft\Windows NT\CurrentVersion\Winlogon
    • b0b2d6e3 = "%Windows%\AppPatch\{random}.dat"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:Windows Explorer"

Step 5

Search and delete the file detected as BKDR_SIMDA.SS

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_SIMDA.SS. 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 these deleted files from backup

*Note: Only Microsoft-related keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.


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