Analysis by: Abraham Latimer Camba

ALIASES:

Troj/Sysmon-D (Sophos), Trojan.SuspectCRC (Ikarus), RDN/Generic.dx!ddr (McAfee), Trojan.Win32.Generic!BT (Sunbelt), Gen:Trojan.Heur.LP.ky8@amu4OPai (Bitdefender)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • 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.

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

  TECHNICAL DETAILS

File Size: 167,936 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 30 Jul 2014

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.

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi
DisplayName = "WMI service provider"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi\Parameters
ServiceDll = "C:\WINDOWS\System32\wbem\raswmi.dll"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi\Enum

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi\Parameters

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\raswmi\Security

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = "{Default values} raswmi"

(Note: The default value data of the said registry entry is {Default values}.)

Backdoor Routine

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

  • Retrieve username of currently logged on Remote Desktop user and impersonates it
  • Enumerate all logical drives
  • Get logical drive’s drive type and disk space
  • Enumerate files and folders
  • Get file’s name, size, attributes and date/time of last modification.
  • Delete files and folders
  • Copy files and folders
  • Read files
  • Download files
  • Upload files
  • Execute files
  • Enumerate processes on the current Remote Desktop Session Host server
  • Get process’ creation, exit, kernel and user time
  • Enumerate all modules of a process
  • Create and terminate processes
  • Perform remote shell
  • Gets the following system information using systeminfo command:
    • Host Name
    • OS Name
    • OS Version
    • OS Manufacturer
    • OS Configuration
    • OS Build Type
    • Registered Owner
    • Registered Organization
    • Product ID
    • Original Install Date
    • System Boot Time
    • System Manufacturer
    • System Model
    • System Type
    • Processor information (processor count and model)
    • BIOS Version
    • Windows Directory location
    • System Directory location
    • Boot Device
    • System Locale
    • Input Locale
    • Time Zone
    • Total Physical Memory
    • Available Physical Memory
    • Virtual Memory information (max, available and in use size)
    • Page File Location
    • Domain
    • Logon Server
    • Hotfixes installed
    • Network Cards installed
    • Connection Name
    • DHCP Enabled
    • DHCP Server
    • IP addresses

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

  • {BLOCKED}.{BLOCKED}.210.49

Other Details

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

  • http://65.55.58.199

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.956.09
FIRST VSAPI PATTERN DATE: 30 Jul 2014
VSAPI OPR PATTERN File: 10.957.00
VSAPI OPR PATTERN Date: 01 Aug 2014

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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\Services
    • raswmi

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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • From: netsvcs = "{Default values} raswmi"
      To: netsvcs = {Default values}

Step 6

Search and delete these files

[ Learn More ]
There may be some 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.
  • C:\WINDOWS\System32\wbem\raswmi.dll

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_MIRAS.B. 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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