Analysis by: Jimelle Monteser
ALIASES:

PWS:Win32/Delf.EM (Microsoft), Win32/PSW.Papras.CX trojan (NOD32)

 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:

  • In the wild: Yes

  OVERVIEW

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 281,208 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 24 Apr 2014

Arrival Details

This backdoor may be dropped by other malware.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "regsvr32.exe "{malware path and file name}""

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CLASSES_ROOT\CLSID\{CLSID 1}

HKEY_CLASSES_ROOT\CLSID\{CLSID 2}

HKEY_CURRENT_USER\Software\Classes\
CLSID\{CLSID 1}

HKEY_CURRENT_USER\Software\Classes\
CLSID\{CLSID 2}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
NoProtectedModeBanner = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
TabProcGrowth = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
2500 = "3"

HKEY_CLASSES_ROOT\CLSID\{CLSID 1}
#cert = "{hex value}"

HKEY_CLASSES_ROOT\CLSID\{CLSID 2}
{random} = "{hex value}"

HKEY_CURRENT_USER\Software\Classes\
CLSID\{CLSID 1}
#cert = "{hex value}"

HKEY_CURRENT_USER\Software\Classes\
CLSID\{CLSID 2}
{random} = "{hex value}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}ally.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}ilix.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}ag.com/viewforum.php?f=51&sid={random}
  • http://[BLOCKED}ld.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}on.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}.{BLOCKED}.32.67/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}.{BLOCKED}.32.80/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}.{BLOCKED}.233.38/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}lon.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}.{BLOCKED}.233.80/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}z.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}pane.com/viewforum.php?f=51&sid={random}
  • http://{BLOCKED}pane.com/viewforum.php?f=51&sid={random}

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.768.01
FIRST VSAPI PATTERN DATE: 01 May 2014
VSAPI OPR PATTERN File: 10.769.00
VSAPI OPR PATTERN Date: 02 May 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

Restart in Safe Mode

[ Learn More ]

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_CLASSES_ROOT\CLSID
    • {CLSID 1}
  • In HKEY_CLASSES_ROOT\CLSID
    • {CLSID 2}
  • In HKEY_CURRENT_USER\Software\Classes\CLSID
    • {CLSID 1}
  • In HKEY_CURRENT_USER\Software\Classes\CLSID
    • {CLSID 2}

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\Run
    • {malware file name} = "regsvr32.exe "{malware path and file name}""
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • NoProtectedModeBanner = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • TabProcGrowth = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • 2500 = "3"

Step 5

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