W32.Appix.D.Worm

When W32.Appix.D.Worm runs, it does the following:

It copies itself as

• C:\%windir%\Appboost.exe. The attributes of this file are set to hidden, read-only, and system.
• C:\%windir%\Appbsvc.exe. The attributes of this file are set to archive.

NOTE: %windir% is a variable. The worm locates the primary Windows installation folder (by default this is C:\Winnt in Windows 2000/NT/XP) and copies itself to that location.

The worm changes the (Default) value of the keys

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\batfile\shell\open\command
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\comfile\shell\open\command
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\cmdfile\shell\open\command
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\exefile\shell\open\command
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\piffile\shell\open\command
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\scrfile\shell\open\command

to

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

so that the worm runs whenever any of the .bat, .com, .cmd, .exe, .pif, or .scr files is executed.

The worm changes the (Default) value of the keys

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices

to

[Default] regedit.exe /s appboost.reg

The worm also adds the values

23 cmd.exe /c dir /s /b C:\*.reg > C:\regs
24 cmd.exe /c for %x in (%Windows%\*.reg %Windows%\System\*.reg Windows%\System32\*.reg) do @copy "%x %y" + %windir%\appboost.reg "%x %y" /y
25 cmd.exe /c for /F "tokens=1*" %x in (C:\regs) do @copy "%x %y" + %windir%\appboost.reg "%x %y" /y
26 regedit.exe /s appboost.reg

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

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."

The worm tries to disable some programs by terminating the active processes and stopping the active services. This is the list of processes that the worm terminates:

• NTIVIR
• AVP32
• AVPCC
• NOD32
• NPSSVC
• NRESQ32
• NSCHED32
• NSCHEDNT
• NSPLUGIN
• NAV
• NAVA
• PSVC
• 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
• SAFEWEB
• WEBSCANX
• ICMON
• CFINET
• AVP.EXE
• ZONEALARM
• AMON.EXE
• PCCIOMON
• PCCMAIN
• POP3TRAP
• WEBTRAP
• AVSYNMGR
• NMAIN
• LUALL
• LUCOMSERVER
• IAMAPP
• ATRACK
• IAMSERV
• PCFWALLICON
• TDS2-98
• TDS2-NT
• VSECOMR
• NISSERV
• NISUM
• F-PROT
• AOL

The worm searches the registry to see whether mIRC is installed on the infected computer. If mIRC is installed, the worm modifies Mirc.ini to send itself to other mIRC users who connect to the same mIRC channel as the infected computer.

The worm retrieves email addresses from files that have the extensions .abd, .doc, .dot, .htm, .log, .rtf, .tbb, .txt, and .wab in all folders.

It searches the registry for the location of the Windows Address Book file, and retrieves email addresses from the file that it finds.

It also searches the registry for the location of The Bat! email program's address book and retrieves email addresses from that file that it finds.

Then it creates the registry key

HKEY_CURRENT_USER\Software\Microsoft\Mails

and keeps the email addresses in this registry key using this format:

<email address 1> 23523
<email address 2> 23523

The worm looks at the following registry key to verify that MAPI is installed on the infected computer

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem\MAPI

It uses the current email program to send itself to all email addresses that it finds.

The worm contains its own SMTP 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 that contains the worm. Information about and a patch for the vulnerability are available at http://www.microsoft.com/technet/security/bulletin/MS01-020.asp.

The email message may have the following characteristics:

Subject: The subject is a combination of

• A nice Screensaver of
• Ein netter Screensaver von
• New Version of
• Eine neue Version von
• Important!:
• Wichtig!:

and

• Pamela Anderson
• Angelina Jolie
• Anna Kournikova
• Porn Screensaver
• Sex ScreenSaver
• TvTool
• Flashget
• WarezBoardAccess
• Undelivarable Email
• Brute Force Tool
• Kündigung (Provider)

Attachment: The attachment may be one of the following:

• PamAnderson.scr
• Jolie.scr
• AnnaKournikova.scr
• XXX.scr
• FreeSex.exe
• TvTool.exe
• FlashGet.exe
• WarezBoardAccess.exe
• Undelivarablemail.exe
• BestTool.exe
• Vertrag.exe

It creates the following files,

• C:\%windir%\Appboost.vbs, which is 4510 bytes in length.
• C:\%windir%\Appboost.reg, which is 1550 bytes in length.

NOTE: Symantec antivirus products detect C:\%windir%\Appboost.vbs as VBS.Bloodhound.Worm.

The worm uses Appboost.vbs to send a copy of itself and the above two files to all contacts in the Outlook Address Book. The email has the following characteristics,

Subject: Application Booster
Message: Try the Free Application Boost Pack, NOW !!!!
Attachments:
Installation Program, which is the worm itself.
Installation Cleanup, which is a copy of C:\%windir%\Appboost.vbs.
Windows 9x/NT/2000 Patch Registry File, which is a copy of C:\%windir%\Appboost.reg.

W32.Appix.C.Worm prepends its pure viral body to all .bat, .com, .cmd, .exe, .scr, .pif, and .msi files in the root of drive C, and to all .exe files in C:\%Windir% folder. It also attempts to prepend its pure viral body to open files. The append body is 233,095 Bytes in length. Besides prepending the viral body to the host files, it also appends eight Bytes that contains the string xiv to the end of the files. The length of each infected file increases 233,103 Bytes.

It infects .php, .phtml and .php3 files in the current folder, C:\%Windir% folder, C:\%System% folder, and in the root of drive C by appending a PHP script. (PHP is a server-side scripting language that is used for dynamic Web page generation).

The viral PHP script infects other .php, .phtml and .php3 files by appending itself to them. If the script finds the infection marker, it does not reinfect the file. The viral PHP script contains 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 Denial of Service (DoS) attack against one of the Web sites. The viral PHP code is designed to download the W32.Appix.D.Worm executable to a client computer that visits an infected Web site.

The worm 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.

The infected .php, .phtml and .php3 files are detected by Symantec antivirus products as PHP.Appix.

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.

Summary