W32.Appix.Worm

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Discovered: September 17, 2002
Updated: February 13, 2007 11:40:32 AM
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154 CAN-2001-0875


W32.Appix.Worm is a worm that attempts to spread across file-sharing networks such as KaZaA and eDonkey2000. The worm infects PHP and PHTML files by appending code that is designed to infect other PHP, PHTML, HTM, and HTML files. It also uploads the W32.Appix.Worm to a client computer that visits the infected Web site. Also, W32.Appix.Worm contains it own SMTP client engine that permits it to replicate using email. The email may arrive with the following characteristics:
Subject: test23
Attachment: Test.scr (175,112 bytes or 176,128 bytes)





Due to buggy code some of the intended features of the worm are never executed. This may result in the display of error messages.

Antivirus Protection Dates

  • Initial Rapid Release version September 17, 2002
  • Latest Rapid Release version March 23, 2017 revision 037
  • Initial Daily Certified version September 17, 2002
  • Latest Daily Certified version March 23, 2017 revision 041
  • Initial Weekly Certified release date September 18, 2002

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

Writeup By: Serghei Sevcenco

Discovered: September 17, 2002
Updated: February 13, 2007 11:40:32 AM
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154 CAN-2001-0875


When W32.Appix.Worm runs, it performs the following actions:

It drops itself using the following file names:

  • %windir%\Appboost.exe
  • %windir%\Appbsvc.exe

NOTE:
%windir% is a variable. The worm locates the Windows main installation folder (by default this is C:\Windows or C:\Winnt) and uses it as a destination folder.

The worm creates the vix or vixsvc mutex. This allows only one instance of the worm to execute in memory.

The worm updates the (Default) value of the key

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile\shell\open\command

with the following contents:

%windir%\appboost.exe "%1" %*

so that it runs whenever an .exe file is executed.

It also creates the value

<random digit, e.g. 6>    <time when the worm was executed in an internal format>

in the registry key

HKEY_CURRENT_USER\Software\Microsoft\Mails

The worm tries to disable some antivirus and firewall programs by terminating the active processes and stopping the active services. This is the list of processes that the worm terminates:
  • _AVP32
  • _AVPCC
  • NOD32
  • NPSSVC
  • NRESQ32
  • NSCHED32
  • NSCHEDNT
  • NSPLUGIN
  • NAV
  • NAVAPSVC
  • NAVAPW32
  • NAVLU32
  • NAVRUNR
  • NAVW32;
  • _AVPM
  • ALERTSVC
  • AMON
  • AVP32
  • AVPCC
  • AVPM
  • N32SCANW
  • NAVWNT;
  • ANTIVIR
  • AVPUPD
  • AVGCTRL
  • AVWIN95
  • SCAN32
  • VSHWIN32
  • F-STOPW;
  • F-PROT95
  • ACKWIN32
  • VETTRAY
  • SWEEP95
  • PCCWIN98
  • IOMON98
  • AVPTC
  • AVE32
  • AVCONSOL
  • FP-WIN
  • DVP95
  • F-AGNT95
  • CLAW95
  • NVC95
  • SCAN
  • VIRUS
  • LOCKDOWN2000
  • NORTON
  • MCAFEE
  • ANTIVIR
  • FIREWAL
  • VET95

If the operating system is Windows 95/98/Me, the worm registers itself as a service process so that it continues to run after you log off. In this case, W32.Appix.Worm will close only when the system is shut down.

If the operating system is Windows NT/2000/XP, the worm creates the appboost service, adds it to the service control manager database, and starts it. The service has the display name "Application Boost Service."

W32.Appix.Worm then composes the file name, which consists of three parts:

The first part is randomly chosen from the following list (spelling errors are preserved):
  • Adobe Photoshop
  • Paintshop Pro
  • Windows XP Coprate
  • Windows XP Proffesional
  • Office XP
  • Quake 3 Online
  • Counter Strike Online
  • Unreal Tournament Online
  • Unreal Tournament 2003 Online
  • Soldier of Fortune Online
  • Soldier of Fortune
  • XBOX Emulator
  • PS2 Emulator
  • GameCube Emulator

The second part is randomly chosen from the following list:
  • Key Generator
  • Serial Generator
  • Crack

The third part, which is an extension, is selected randomly from this list:
  • .zip.exe
  • .rar.exe
  • .ace.exe
  • .rar.exe
  • .exe
  • .pif
  • .cmd
  • .bat
  • .hta

As a result, the composed file name may look this: Adobe Photoshop Crack.rar.exe

The worm then copies itself using the composed file name into the shared folders of the KaZaA and Edonkey2000 software. If it finds a folder named Download or Downloads on drives C and D, it drops itself there, as well.

The worm contains its own SMTP client engine, which allows it to submit itself in the form of an email message. The worm exploits a vulnerability in Microsoft Outlook and Outlook Express in an attempt to execute itself when you open or even preview the message in which it is contained. Information and a patch for the vulnerability are available at http://www.microsoft.com/technet/security/bulletin/MS01-020.asp .

The worm contains code that may construct and submit an email message in the following form:
Attachment: Test.scr (175,112 bytes or 176,128 bytes)
Subject: test23

The worm enumerates files on fixed drives C and D. If it locates a PHP or PHTML file, it appends it with a PHP script (PHP is a server-side scripting language that is used for dynamic Web page generation). The infected PHP/PHTML files are detected by Symantec antivirus product as PHP.Appix.

The viral PHP-script enumerates files that exist in the same folder as the infected file and infects other PHP and PHTML files by appending itself. The infection is not performed, if the infection marker is found. For every HTM or HTML file, it appends an exploit code that may cause your browser or the operating system to stop responding. The exploit code is based on infinite loops that consume resources. It may also perform a DoS attack against one of the Web sites. The viral PHP code is designed to upload the W32.Appix.Worm executable to the client computer that visits the infected Web site. It exploits the "File Name Spoofing Vulnerability." Information and a patch for the vulnerability are available at http://www.microsoft.com/technet/security/bulletin/MS01-058.asp .

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.

Writeup By: Serghei Sevcenco

Discovered: September 17, 2002
Updated: February 13, 2007 11:40:32 AM
Type: Worm
Systems Affected: Windows
CVE References: CVE-2001-0154 CAN-2001-0875


NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Do one of the following:
    • Windows 95/98/Me: Restart the computer in Safe mode.
    • Windows NT/2000/XP: Stop the worm process.
  2. Reverse the changes that the worm made to the registry.
  3. Do one of the following:
    • Windows 95/98/Me: Restart the computer in normal mode.
    • Windows NT/2000/XP: Restart your Symantec antivirus product.
  4. Update the virus definitions.
  5. Run a full system scan, and delete all files that are detected as W32.Appix.Worm or PHP.Appix.
For details on how to do this, read the following instructions.

To restart the computer in Safe mode or end the worm process:

Windows 95/98/Me
Restart the computer in Safe mode. All Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document How to start the computer in Safe Mode .

Windows NT/2000/XP
To stop the worm process:
  1. Press Ctrl+Alt+Delete one time.
  2. Click Task Manager.
  3. Click the Processes tab.
  4. Double-click the Image Name column header to sort the processes alphabetically.
  5. Scroll through the list, and look for the following names:
    • AppBoostTrojan (Please note that only 15 characters are displayed.)
    • Appboost.exe
  6. For each of these processes that you find, click the name, and then click End Process.
  7. Close the Task Manager.

To reverse the changes that the worm made to the registry:

CAUTION
: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  1. Navigate to and select the following key:

    HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command

    CAUTION: The HKEY_LOCAL_MACHINE\Software\Classes key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with an .exe extension from running. Make sure that you browse all the way along this path until you reach the \command subkey.

    Make sure that you modify the HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command subkey that is shown in the following figure:

    <<=== NOTE: Modify this key.
  2. In the right pane, double-click the (Default) value.
  3. Delete the current value data, and then type: "%1" %* (That is, type the following characters: quote-percent-one-quote-space-percent-asterisk.)

    NOTES:
    • Under Windows 95/98/Me/NT, the Registry Editor automatically encloses the value within quotation marks. When you click OK, the (Default) value should look exactly like this:

      ""%1" %*"  
    • Under Windows 2000/XP, the additional quotation marks will not appear. When you click OK, the (Default) value should look exactly like this:

      "%1" %*
    • Make sure that you completely delete all value data in the command key before you type the correct data. If you leave a space at the beginning of the entry, any attempt to run program files will result in the error message, "Windows cannot find .exe." If this happens to you, start over at the beginning of this document, and make sure that you completely remove the current value data.
  4. Navigate to the key

    HKEY_CURRENT_USER\Software\Microsoft\Mails
  5. In the right pane, delete the value

    <random digit, e.g. 6>    <time when the worm was executed in an internal format>
  6. Exit the Registry Editor.

To restart the computer or antivirus product:
Do one of the following:
  • Windows 95/98/Me: Restart the computer as you normally would. Do not choose Safe mode this time, and allow the computer to start normally.
  • Windows NT/2000/XP: Restart your Symantec antivirus product. The method for doing this depends on the product. Please see the product documentation for additional information.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers one time each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
  • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

    Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with W32.Appix.Worm or PHP.Appix, click Delete.


Writeup By: Serghei Sevcenco