TROJ_ZLOB.EFV

July 25, 2013
 ALIASES:

Trojan.Zlob (Symantec); Trojan-Downloader.Win32.Zlob.bosc (Kaspersky); Trojan.Win32.Generic.pak!cobra (Sunbelt); Trojan horse Downloader.Zlob (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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

File Size:

109,482 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

17 Jun 2013

Arrival Details

This Trojan 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 Trojan creates the following folders:

  • %Program Files%\VideoAccessCodec
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsv7.tmp
  • %User Profile%\Network\Downloader

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\nsz1.tmp
  • %User Temp%\nsv7.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
VideoPlugin

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS\CtlGuid

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\BITS

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
VideoPlugin
pn = "5"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
VideoPlugin
sid = "502"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
VideoPlugin
aid = "205"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
VideoPlugin
said = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS
LogSessionName = "stdout"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS
Active = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS
ControlFlags = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS\CtlGuid
Guid = "4a8aaa94-cfc4-46a7-8e4e-17bc45608f0a"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Tracing\
Microsoft\BITS\CtlGuid
BitNames = "{random characters}"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\BackupRestore\FilesNotToBackup
BITS_metadata = "%User Profile%\Downloader\*"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\nsz3.tmp
  • %Program Files%\VideoAccessCodec\install.ico
  • %User Temp%\nsv7.tmp\System.dll
  • %Program Files%\VideoAccessCodec\hipgxf.exe
  • %Program Files%\VideoAccessCodec\imex.bat
  • %User Temp%\nsv7.tmp\NSISdl.dll
  • %Program Files%\VideoAccessCodec\VideoAccessCodec.ocx

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}workcom.com/dw.php?{random characters}

This report is generated via an automated analysis system.

  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

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\Software\Microsoft
    • VideoPlugin
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft
    • BITS
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS
    • CtlGuid
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    • BITS

Step 3

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_LOCAL_MACHINE\SOFTWARE\Microsoft\VideoPlugin
    • pn = "5"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VideoPlugin
    • sid = "502"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VideoPlugin
    • aid = "205"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VideoPlugin
    • said = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS
    • LogSessionName = "stdout"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS
    • Active = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS
    • ControlFlags = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS\CtlGuid
    • Guid = "4a8aaa94-cfc4-46a7-8e4e-17bc45608f0a"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Tracing\Microsoft\BITS\CtlGuid
    • BitNames = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\BackupRestore\FilesNotToBackup
    • BITS_metadata = "%User Profile%\Downloader\*"

Step 4

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %User Temp%\nsz3.tmp
  • %Program Files%\VideoAccessCodec\install.ico
  • %User Temp%\nsv7.tmp\System.dll
  • %Program Files%\VideoAccessCodec\hipgxf.exe
  • %Program Files%\VideoAccessCodec\imex.bat
  • %User Temp%\nsv7.tmp\NSISdl.dll
  • %Program Files%\VideoAccessCodec\VideoAccessCodec.ocx

Step 5

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.
  • %Program Files%\VideoAccessCodec
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsv7.tmp
  • %User Profile%\Network\Downloader

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZLOB.EFV. 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 7

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\nsz1.tmp
  • %User Temp%\nsv7.tmp


Did this description help? Tell us how we did.