TROJ_FAKEAV.PFL

 Analysis by: Sabrina Lei Sioting

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

It employs registry shell spawning by adding certain registry entries. This allows this malware to execute even when other applications are opened.

It modifies certain registry entries to disable Security Center functions. Doing this allows this malware to execute its routines without being detected. It modifies registry entries to disable the Windows Firewall settings. This action allows this malware to perform its routines without being deteted by the Windows Firewall.

It deletes the initially executed copy of itself.

It displays fake alerts that warn users of infection. It also displays fake scanning results of the affected system. It then asks for users to purchase it once scanning is completed. If users decide to purchase the rogue product, users are directed to a certain website asking for sensitive information, such as credit card numbers.

  TECHNICAL DETAILS

File Size:

342,016 bytes

Memory Resident:

Yes

Initial Samples Received Date:

04 Jan 2011

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 drops the following copies of itself into the affected system:

  • %Application Data%\{random}.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It drops the following files:

  • %System Root%\Documents and Settings\All Users\Application Data\{random}
  • %Application Data%\{random}
  • %User Temp%\{random}
  • %User Profile%\Templates\{random}

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.. %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.. %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Autostart Technique

This Trojan employs registry shell spawning to ensure its execution when certain file types are accessed by adding the following entries:

HKEY_CLASSES_ROOT\2Xy\shell\
open\command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

HKEY_CLASSES_ROOT\K5o\shell\
open\command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

HKEY_CLASSES_ROOT\.exe\shell\
open\command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

HKEY_CURRENT_USER\Software\Classes\
.exe
{default} = "2Xy"

HKEY_CURRENT_USER\Software\Classes\
.exe\shell\open\
command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

HKEY_CURRENT_USER\Software\Classes\
2Xy\shell\open\
command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

HKEY_CURRENT_USER\Software\Classes\
K5o\shell\open\
command
{default} = ""%Application Data%\{random}.exe" -a "%1" %*"

Other System Modifications

This Trojan modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\
StartMenuInternet\FIREFOX.EXE\shell\
open\command
{default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Mozilla Firefox\firefox.exe""

(Note: The default value data of the said registry entry is "%Program Files%\Mozilla Firefox\firefox.exe".)

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\
StartMenuInternet\FIREFOX.EXE\shell\
safemode\command
{default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode"

(Note: The default value data of the said registry entry is ""C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode".)

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\
StartMenuInternet\IEXPLORE.EXE\shell\
open\command
{default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Internet Explorer\iexplore.exe""

(Note: The default value data of the said registry entry is ""C:\Program Files\Internet Explorer\iexplore.exe"".)

HKEY_CLASSES_ROOT\.exe
{default} = "2Xy"

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

It adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\2Xy

HKEY_CLASSES_ROOT\K5o

HKEY_CURRENT_USER\Software\Classes\
2Xy

HKEY_CURRENT_USER\Software\Classes\
K5o

It modifies the following registry entries to disable Security Center functions:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusDisableNotify = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
AntiVirusOverride = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallDisableNotify = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
FirewallOverride = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Security Center
UpdatesDisableNotify = 1

(Note: The default value data of the said registry entry is 0.)

It modifies the following registry entries to disable the Windows Firewall settings:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
EnableFirewall = 0

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile
DisableNotifications = 1

(Note: The default value data of the said registry entry is 0.)

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
EnableFirewall = 0

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
DoNotAllowExceptions = 0

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile
DisableNotifications = 1

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.com/1006000513
  • http://{BLOCKED}.com/100600051336417543823

It deletes the initially executed copy of itself

Rogue Antivirus Routine

This Trojan displays fake alerts that warn users of infection. It also displays fake scanning results of the affected system. It then asks for users to purchase it once scanning is completed. If users decide to purchase the rogue product, users are directed to a certain website asking for sensitive information, such as credit card numbers.

  SOLUTION

Minimum Scan Engine:

8.900

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 terminate files detected as TROJ_FAKEAV.PFL

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CLASSES_ROOT
    • 2Xy
  • In HKEY_CLASSES_ROOT
    • K5o
  • In HKEY_CURRENT_USER\Software\Classes
    • 2Xy
  • In HKEY_CURRENT_USER\Software\Classes
    • K5o

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\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile
    • DoNotAllowExceptions = 0
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile
    • DisableNotifications = 1
  • In HKEY_CLASSES_ROOT\.exe\shell\open\command
    • {default} = ""%Application Data%\{random}.exe" -a "%1" %*"
  • In HKEY_CURRENT_USER\Software\Classes\.exe
    • {default} = "2Xy"
  • In HKEY_CURRENT_USER\Software\Classes\.exe\shell\open\command
    • {default} = ""%Application Data%\{random}.exe" -a "%1" %*"

Step 5

Delete these registry values

[ 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_MACHINESOFTWAREMicrosoftSecurity Center

    • FirewallDisableNotify = "1"
    • UpdatesDisableNotify = "1"
    • AntiVirusDisableNotify = "1"
    • AntiVirusOverride = "1"
    • FirewallOverride = "1"
  • In HKEY_LOCAL_MACHINESOFTWAREPolicies
    MicrosoftWindowsFirewallDomainProfile

    • EnableFirewall = "0"
  • In HKEY_LOCAL_MACHINESOFTWAREPolicies
    MicrosoftWindowsFirewall StandardProfile

    • EnableFirewall = "0"
  • In HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoft
    WindowsWindowsUpdate

    • DoNotAllowXPSP2 = "1"

Step 6

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_CLASSES_ROOT\.exe
    • From: {default} = "2Xy"
      To: {default} = "exefile"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\FIREFOX.EXE\shell\open\command
    • From: {default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Mozilla Firefox\firefox.exe""
      To: {default} = "%Program Files%\Mozilla Firefox\firefox.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\FIREFOX.EXE\shell\safemode\command
    • From: {default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode"
      To: {default} = ""C:\Program Files\Mozilla Firefox\firefox.exe" -safe-mode"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\IEXPLORE.EXE\shell\open\command
    • From: {default} = ""%Application Data%\{random}.exe" -a "C:\Program Files\Internet Explorer\iexplore.exe""
      To: {default} = ""C:\Program Files\Internet Explorer\iexplore.exe""
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
    • From: DisableNotifications = 1
      To: DisableNotifications = 0

Step 7

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.
  • %System Root%\Documents and Settings\All Users\Application Data\{random}
  • %Application Data%\{random}
  • %User Temp%\{random}
  • %User Profile%\Templates\{random}

Step 8

Scan your computer with your Trend Micro product to delete files detected as TROJ_FAKEAV.PFL. 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.


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