Analysis by: Pearl Charlaine Espejo
 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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 deletes itself after execution.

  TECHNICAL DETAILS

File Size: 241,152 bytes
File Type: DLL
Memory Resident: Yes
Initial Samples Received Date: 17 Aug 2016

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 files:

  • %Application Data%\{random folder name}\{random filename 2}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following copies of itself into the affected system:

  • %Application Data%\{random folder name}\{random filename 1}.dll

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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
{random key} = "regsvr32.exe "%Application Data%\{random folder name}\{random filename 1}.dll""

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\{CLSID}

HKEY_CURRENT_USER\Software\{CLSID}\
{random folder name}

HKEY_CURRENT_USER\Software\{CLSID}\
{random folder name}\1669

It adds the following registry entries:

HKEY_CURRENT_USER\Software\{CLSID}\
{random folder name}\1669
{random} = "{hex values}"

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"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}ee.com/rss/feed/stream
  • http://{BLOCKED}sei.com/rss/feed/stream
  • http://{BLOCKED}g.com/rss/feed/stream
  • http://{BLOCKED}zei.net/rss/feed/stream
  • http://{BLOCKED}s.com/rss/feed/stream
  • http://{BLOCKED}oo.com/rss/feed/stream
  • http://{BLOCKED}r.com/rss/feed/stream
  • http://{BLOCKED}hid.com/rss/feed/stream
  • http://{BLOCKED}al.com/rss/feed/stream
  • http://{BLOCKED}ie.com/rss/feed/stream

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.720.05
FIRST VSAPI PATTERN DATE: 17 Aug 2016
VSAPI OPR PATTERN File: 12.721.00
VSAPI OPR PATTERN Date: 18 Aug 2016

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 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\{CLSID}\{random folder name}\1669
    • {random} = "{hex values}"
  • 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"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random numbers} = "regsvr32.exe "%Application Data%\{random folder name}\{random filename 1}.dll""

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_VAWTRAK.PE. 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 6

The following created files/folders/registry keys/registry entries cannot be identified by the user since there are no reference values in the created key. The only way it can be identified is by comparing the present system information with a backup. Note that the said components do not have to be deleted since it won't be harmful to the system.

  • %Application Data%\{random folder name}\{random filename 2}
  • HKEY_CURRENT_USER\Software\{CLSID}
  • HKEY_CURRENT_USER\Software\{CLSID}\{random folder name}


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