TROJ_ZLOB.DLY

June 22, 2013
 ALIASES:

TrojanDownloader:Win32/Zlob (Microsoft); Trojan.Emcodec (Symantec); PAK:UPX, ARC:NSIS, [$PLUGINSDIR\isecur.dll]:Trojan-Downloader.Win32.Zlob.ayr (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)

 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:

55,445 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

13 Oct 2012

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:

  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Temp%\nsu3.tmp
  • %Program Files%\Perfect Codec

(Note: %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.. %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 System Modifications

This Trojan deletes the following files:

  • %User Temp%\nsf1.tmp
  • %User Temp%\nsu3.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_CURRENT_USER\Software\Internet Security

HKEY_CLASSES_ROOT\AVZipEnchancer.Chl\CLSID

HKEY_CLASSES_ROOT\CodecsSoftwarePackage.chl\CLSID

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Internet Security
Type = "3"

HKEY_CURRENT_USER\Software\Internet Security
Path = "%Program Files%\Perfect Codec"

HKEY_CURRENT_USER\Software\Internet Security
Removable = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
ProductionEnvironment = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
DisplayName = "Perfect Codec 4.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
UninstallString = "%Program Files%\Perfect Codec\uninst.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
DisplayIcon = "%Program Files%\Perfect Codec\uninst.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
DisplayVersion = "4.0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
URLInfoAbout = "www.perfectcodec.com"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Uninstall\
Perfect Codec
Publisher = "Perfect Codec Software"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\nsu2.tmp
  • %User Temp%\nsu3.tmp\page.ReInstallUninstall.ini
  • %User Temp%\nsu3.tmp\ioSpecial.ini
  • %User Temp%\nsu3.tmp\modern-wizard.bmp
  • %User Temp%\nsu3.tmp\modern-header.bmp
  • %User Temp%\nsu3.tmp\isecur.dll
  • %Program Files%\Perfect Codec\uninst.exe
  • %User Temp%\nsu3.tmp\InstallOptions.dll

(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).)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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_CURRENT_USER\Software\
    • Internet Security
  • In HKEY_CLASSES_ROOT\AVZipEnchancer.Chl
    • CLSID
  • In HKEY_CLASSES_ROOT\CodecsSoftwarePackage.chl
    • CLSID
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall
    • Perfect Codec

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_CURRENT_USER\Software\Internet Security
    • Type = "3"
  • In HKEY_CURRENT_USER\Software\Internet Security
    • Path = "%Program Files%\Perfect Codec"
  • In HKEY_CURRENT_USER\Software\Internet Security
    • Removable = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • ProductionEnvironment = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • DisplayName = "Perfect Codec 4.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • UninstallString = "%Program Files%\Perfect Codec\uninst.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • DisplayIcon = "%Program Files%\Perfect Codec\uninst.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • DisplayVersion = "4.0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • URLInfoAbout = "www.perfectcodec.com"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Perfect Codec
    • Publisher = "Perfect Codec Software"

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%\nsu2.tmp
  • %User Temp%\nsu3.tmp\page.ReInstallUninstall.ini
  • %User Temp%\nsu3.tmp\ioSpecial.ini
  • %User Temp%\nsu3.tmp\modern-wizard.bmp
  • %User Temp%\nsu3.tmp\modern-header.bmp
  • %User Temp%\nsu3.tmp\isecur.dll
  • %Program Files%\Perfect Codec\uninst.exe
  • %User Temp%\nsu3.tmp\InstallOptions.dll

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.
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Temp%\nsu3.tmp
  • %Program Files%\Perfect Codec

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_ZLOB.DLY. 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%\nsf1.tmp
  • %User Temp%\nsu3.tmp


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