W32.Petch

Risk Level 1: Very Low

Discovered: October 26, 2003

Updated: February 13, 2007 12:12:43 PM

Also Known As: IRC-Worm.Fagot [Kaspersky], Fagot [F-Secure], IRC.Trojan.Fgt

Type: Worm

Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP

SUMMARY

W32.Petch is a downloaded file that disables firewall and security software. This worm also deletes critical system files and changes the Internet Explorer home page to a pornographic page.

A Web site responsible for distributing this threat is no longer available.

This threat is UPX-packed and written in the Delphi programming language.

Virus definitions dated prior to October 31, 2003 may detect this threat as IRC.Trojan.Fgt.

Protection

Initial Rapid Release version October 27, 2003
Latest Rapid Release version August 20, 2008 revision 017
Initial Daily Certified version October 27, 2003
Latest Daily Certified version January 20, 2009 revision 048
Initial Weekly Certified release date October 29, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment

Wild

Wild Level: Low
Number of Infections: 0 - 49
Number of Sites: 0 - 2
Geographical Distribution: Medium
Threat Containment: Easy
Removal: Difficult

Damage

Damage Level: High

Distribution

Distribution Level: Low

TECHNICAL DETAILS

When W32.Petch runs, it performs the following actions:

Copies itself as:
- C:\Windows\System32\Userinit32.exe
- C:\Windows\System32\Dllhost32.exe
- C:\Windows\Notepad.exe
- C:\Windows\Regedit.exe
  
  Note: These values are hard-coded and do not depend on system variables.
Changes the value to:

"Userinit"="C:\Windows\system32\userinit32.exe"

in the registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
Adds the value that refers to:

C:\Windows\system32\dllhost32.exe

to the registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
Searches for and disables the following processes and programs:
- _Avp32.exe
- _avpcc.exe
- _avpm.exe
- Avnt.exe
- Avp.exe
- Blackice.exe
- Blackice.exe
- Ccevtmgr.exe
- Ccsetmgr.exe
- Fprot.exe
- Fp-win.exe
- Fsav32.exe
- Fsgk32.exe
- Fsm32.exe
- Fsma32.exe
- Fsma32.exe
- Fsmb32.exe
- Fsmb32.exe
- Fssm32.exe
- Fwenc.exe
- Kavlite40eng.exe
- Kavpers40eng.exe
- N32scanw.exe
- Nav auto-protect
- Navapsvc.exe
- Navapw32.exe
- Navw32.exe
- Nmain.exe
- Normist.exe
- Norton_internet_secu_3.0_407.exe
- Npf40_tw_98_nt_me_2k.exe
- Npfmessenger.exe
- Nprotect.exe
- Npssvc.exe
- Nsched32.exe
- Ntvdm.exe
- Pavcl.exe
- Pavsched.exe
- Wfindv32.exe
- Zapro.exe
- Zapsetup3001.exe
- Zatutor.exeZauinst.exe
- Zonalm2601.exe
- Zonealarm.exe
Deletes the following registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Desktop\SafeMode HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\SafeBoot HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Control\SafeBoot HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices HKEY_LOCAL_MACHINE\SYSTEM\LastKnownGoodRecovery HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\ContentIndex\Catalogs\System HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Biosinfo
Resets the Internet Explorer home page by changing the registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\Start Page

to a value of www.blacksnake.com, which is a Web site that contains pornographic material.
Sets the default user name and the alternate default user name to C**K_S******G_F****T
Deletes the following files:
- C:\ Windows \System32\Userinit.exe
- C:\Windows\Cmd.exe
- C:\Windows\Notepad.exe
- C:\Windows\Notepad.exe
- C:\Windows\Regedit.exe
- C:\Windows\Regedit.exe
- C:\Windows\System32\Alg.exe
- C:\Windows\System32\Alg.exe
- C:\Windows\System32\Autochk.exe
- C:\Windows\System32\Autochk.exe
- C:\Windows\System32\Bootok.exe
- C:\Windows\System32\Bootok.exe
- C:\Windows\System32\Chcp.exe
- C:\Windows\System32\Chcp.exe
- C:\Windows\System32\Chkdsk.exe
- C:\Windows\System32\Chkntfs.exe
- C:\Windows\System32\Chkntfs.exe
- C:\Windows\System32\Ctfmon.exe
- C:\Windows\System32\Ctfmon.exe
- C:\Windows\System32\Dumprep.exe
- C:\Windows\System32\Dumprep.exe
- C:\Windows\System32\Imapi.exe
- C:\Windows\System32\Imapi.exe
- C:\Windows\System32\Logon.exe
- C:\Windows\System32\Logon.exe
- C:\Windows\System32\MDM.exe
- C:\Windows\System32\MDM.exe
- C:\Windows\System32\Ntkrnlpa.exe
- C:\Windows\System32\Ntkrnlpa.exe
- C:\Windows\System32\Ntoskrnl.exe
- C:\Windows\System32\Ntoskrnl.exe
- C:\Windows\System32\Progman.exe
- C:\Windows\System32\Progman.exe
- C:\Windows\System32\Recover.exe
- C:\Windows\System32\Recover.exe
- C:\Windows\System32\Regedt32.exe
- C:\Windows\System32\Regsvr32.exe
- C:\Windows\System32\Services.exe
- C:\Windows\System32\Services.exe
- C:\Windows\System32\Shutdown.exe
- C:\Windows\System32\Shutdown.exe
- C:\Windows\System32\Systray.exe
- C:\Windows\System32\Systray.exe
- C:\Windows\System32\Taskman.exe
- C:\Windows\System32\Taskmgr.exe
- C:\WINDOWS\System32\Userinit.exe
- C:\Windows\System32\Win.exe
- C:\Windows\System32\Win.exe
- C:\Windows\System32\Wowexec.exe
- C:\Windows\System32\Wowexec.exe
- C:\Windows\System32\Wuauclt.exe
- C:\Windows\System32\Wuauclt.exe
- C:\Windows\TASKMAN.exe
  
  Note: These paths are hard-coded and do not depend on system variables. If the worm deletes these files, in most cases, Windows will no longer run when the computer is restarted.
Removes most, if not all, of the subkey paths from the following registry subkeys of HKEY_LOCAL_MACHINE:

HARDWARE SECURITY SOFTWARE SYSTEM Software System
Displays the fake error message:

Error in memory block: #A5487F
Runs mIRC and executes a one-line command with the message "...//************/britney.jpg <- uuh, check it out !! :D"

If ActiveX controls are enabled when the file is downloaded, it will execute. Since firewall protection is disabled, there is no other warning about ActiveX applications.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
For further information on the terms used in this document, please refer to the Security Response glossary.

REMOVAL

These removal instructions will work if W32.Petch has not yet been executed.

If W32.Petch has already been executed, it is likely that you will no longer be able to start Windows. While the damage that W32.Petch does varies with the installation path, once it runs, it makes numerous changes to the registry and deletes system files.

In this situation, replace the deleted files and the Windows registry either from a clean backup, or re-install the operating system.

Once you have replaced the registry with a clean copy and have restored any missing system files, update the virus definitions and run a full system scan as described in the next section.

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

Disable System Restore (Windows Me/XP).
Update the virus definitions.
Run a full system scan and delete all the files detected as W32.Petch.

For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. Updating the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:

Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. Scanning for and deleting the infected files

Start your Symantec antivirus program and make sure that it is configured to scan all the files.
- For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
- For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
Run a full system scan.
If any files are detected as infected with W32.Petch, click Delete.