WORM_AUTORUN.FLD


 ALIASES:

Worm:Win32/Renocide.Y (Microsoft); W32/Autorun.worm.zf.gen (McAfee); Trojan Horse (Symantec); PAK:UPX, ARC:Embedded, [script.au3]:Trojan.Win32.Autoit.afk, [40E04BCACA55A12B.au3.tbl.decoded]:Worm (Kaspersky); Trojan.Win32.AutoIt.gen.1 (v) (Sunbelt); Trojan-Downloader:W32/AutoIt.BI (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm 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:

574,362 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

17 Mar 2012

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system:

  • %System%\csrcs.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunServices
csrcs = "%System%\csrcs.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe csrcs.exe"

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

Other System Modifications

This worm deletes the following files:

  • %User Temp%\s.cmd

(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.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\
DRM\amty

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\RunServices

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DRM\amty
ilop = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
csrcs = "%System%\csrcs.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DRM\amty
fix1 = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\advapi32.dll[MofResourceName] = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\DRIVERS\ACPI.sys[ACPIMOFResource] = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\DRIVERS\mssmbios.sys[MofResource] = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\DRIVERS\intelppm.sys[PROCESSORWMI] = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\DRIVERS\ipnat.sys[IPNATMofResource] = "{random characters}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
WBEM\WDM
%System%\Drivers\HTTP.sys[UlMofResource] = "{random characters}"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

(Note: The default value data of the said registry entry is 2.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
SuperHidden = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = "1"

(Note: The default value data of the said registry entry is 1.)

Dropping Routine

This worm drops the following files:

  • %User Temp%\aut1.tmp
  • %User Temp%\poytxgz
  • %User Temp%\aut2.tmp
  • %User Temp%\cficyab

(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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and delete files detected as WORM_AUTORUN.FLD using either the Startup Disk or Recovery Console

[ 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_LOCAL_MACHINE\Software\Microsoft\DRM
    • amty
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
    • RunServices
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
    • csrcs = "%System%\csrcs.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DRM\amty
    • ilop = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • csrcs = "%System%\csrcs.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DRM\amty
    • fix1 = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\advapi32.dll[MofResourceName] = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\DRIVERS\ACPI.sys[ACPIMOFResource] = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\DRIVERS\mssmbios.sys[MofResource] = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\DRIVERS\intelppm.sys[PROCESSORWMI] = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\DRIVERS\ipnat.sys[IPNATMofResource] = "{random characters}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WBEM\WDM
    • %System%\Drivers\HTTP.sys[UlMofResource] = "{random characters}"

Step 5

Restore this modified 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\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = ""2""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • SuperHidden = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
    • From: CheckedValue = "1"
      To: CheckedValue = ""1""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe csrcs.exe"
      To: Shell = ""Explorer.exe""

Step 6

Search and delete these files

[ Learn More ]
There may be some component files 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%\aut1.tmp
  • %User Temp%\poytxgz
  • %User Temp%\aut2.tmp
  • %User Temp%\cficyab

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_AUTORUN.FLD. 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 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%\s.cmd


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