BKDR_SIMDA.SB
PWS:Win32/Simda.D (Microsoft), W32/Shiz.A.gen!Eldorado (Authentium), W32/Shiz.HPH!tr (Fortinet), Win32/Spy.Shiz.NCB (Eset),
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Backdoor
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
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.
TECHNICAL DETAILS
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 or C:\WINNT.)
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"
Other Details
This backdoor connects to the following possibly malicious URL:
- http://{BLOCKED}.com/login.php
SOLUTION
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
Identify and delete files detected as BKDR_SIMDA.SB using either the Startup Disk or Recovery Console
Step 3
Restore this modified registry value
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,"
- From: Userinit = "%System%\userinit.exe, %Windows%\AppPatch\{random}.dat,"
Step 4
Delete this registry value
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"
- 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"
- {malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:Windows Explorer"
Step 5
Scan your computer with your Trend Micro product to delete files detected as BKDR_SIMDA.SB. 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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