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BKDR_ZACCESS.PPY

February 08, 2014
 Analysis by: Adrian Cofreros
 ALIASES:

TrojanDropper:Win32/Sirefef.gen!B(Microsoft),HEUR:Trojan.Win32.Generic(Kaspersky),Trojan.Zeroaccess!g35(Norton)

 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 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 then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

179,200 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Jan 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.

Installation

This backdoor drops the following files:

  • %System Root%\RECYCLER\S-1-5-18\${random}\n
  • %System Root%\RECYCLER\S-1-5-18\${random}\@
  • %System Root%\RECYCLER\{SID}\${random}\n
  • %System Root%\RECYCLER\{SID}\${random}\@

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

  • %System Root%\RECYCLER\S-1-5-18\${random}
  • %System Root%\RECYCLER\S-1-5-18\${random}\L
  • %System Root%\RECYCLER\S-1-5-18\${random}\U
  • %System Root%\RECYCLER\{SID}\${random}
  • %System Root%\RECYCLER\{SID}\${random}\L
  • %System Root%\RECYCLER\{SID}\${random}\U

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It executes then deletes itself afterward.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Classes\
CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InprocServer32
{Default} = "%System Root%\RECYCLER\{SID}\${random}\n."

It modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_CLASSES_ROOT\CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\
InprocServer32
{Default} = "%System Root%\RECYCLER\S-1-5-18\${random}\n."

(Note: The default value data of the said registry entry is %System%\wbem\fastprox.dll.)

HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\
InProcServer32
{Default} = "%System Root%\RECYCLER\{SID}\${random}\n."

(Note: The default value data of the said registry entry is %System%\SHELL32.dll.)

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\InprocServer32
{Default} = "%System Root%\RECYCLER\S-1-5-18\${random}\n."

(Note: The default value data of the said registry entry is %System%\wbem\fastprox.dll.)

Other System Modifications

This backdoor modifies the following registry entries:

HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\
InProcServer32
ThreadingModel = "Both"

(Note: The default value data of the said registry entry is Apartment.)

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_WSCSVC

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_SHAREDACCESS

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\wscsvc

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}nd.com/app/geoip.js

NOTES:
It connects to randomly and possibly malicious URLs.

  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

Scan your computer with your Trend Micro product and note files detected as BKDR_ZACCESS.PPY

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\Classes\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InprocServer32
    • {Default} = "%System Root%\RECYCLER\{SID}\${random}\n."

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InProcServer32
    • From: ThreadingModel = "Both"
      To: ThreadingModel = Apartment
  • In HKEY_CLASSES_ROOT\CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\InprocServer32
    • From: {Default} = "%System Root%\RECYCLER\S-1-5-18\${random}\n."
      To: {Default} = %System%\wbem\fastprox.dll
  • In HKEY_CLASSES_ROOT\CLSID\{fbeb8a05-beee-4442-804e-409d6c4515e9}\InProcServer32
    • From: {Default} = "%System Root%\RECYCLER\{SID}\${random}\n."
      To: {Default} = %System%\SHELL32.dll
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{5839FCA9-774D-42A1-ACDA-D6A79037F57F}\InprocServer32
    • From: {Default} = "%System Root%\RECYCLER\S-1-5-18\${random}\n."
      To: {Default} = %System%\wbem\fastprox.dll
RESTORE
  • Close Registry Editor.

    • Step 6

    Search and delete these folders

    [ Learn More ]
    Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden folders in the search result.
    • %System Root%\RECYCLER\S-1-5-18\${random}
    • %System Root%\RECYCLER\{SID}\${random}

    Step 7

    Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZACCESS.PPY. 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 8

    Restore these deleted registry keys/values from backup

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

    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
      • LEGACY_WSCSVC
    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
      • LEGACY_SHAREDACCESS
    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
      • wscsvc
    • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
      • SharedAccess


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