W32.Klez.H@mm is a modified variant worm of W32.Klez.E@mm

My Norton antivirus program just intercepted an e-mail from an innocent sounding source that I did not recognize, said there was a W32.Klez.H@mm virus and deleted the e-mail. Then I opened your news letter and found this message. See, these things can hit us at home .... will keep the antivirus programs up to date and thanks for your news letter.

"W32.Klez.H@mm is a modified variant worm of W32.Klez.E@mm. The worm is capble of infecting files and can spread by email & network shares. This worm infects executable files and randomly chooses a file from the machine to send with it. The worm is ranked Category 4 - Severe, this is a dangerous threat and difficult to contain"

Also, thanks for your Scottsdale location on FLW. It is very convenient (beats driving th crazy 101 to Tempe) and they do a great repair job. And now I will be sure to read ALL your news letters with care .. .. it's a little scarry to think I was so close to a really bad virus.

Ben Ornburn, Scottsdale

[email protected]

This question was answered on January 4, 2005. Much of the information contained herein may have changed since posting.

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The W32.Klez.H@mm worm is a modified variant of the W32.Klez.E@mm This variant can spread by email and network shares This worm can also infect files.

Removal tool

Symantec has provided a tool to remove the infections of all the known variants of W32.Klez and W32.ElKern Try this removal tool first, as it is the easiest way to remove the threats.

Note on W32.Klez.gen@mm detections

W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez Computers that are infected with W32.Klez.gen@mm have most likely been exposed to either W32.Klez.E@mm or W32.Klez.H@mm If your computer is detected as infected with W32.Klez.gen@mm, download and run the tool In most cases, the tool will be able to remove the infection.

Also Known As: W32/Klez.h@MM [McAfee], WORM_KLEZ.H [Trend], WORM_KLEZ.I [Trend], I-Worm.Klez.h [Kaspersky], Klez.H, W32/Klez-H [Sophos], Win32.Klez.H [Computer Associates], W32/Klez.I [Panda], W32/Klez.H@mm [Frisk]

Type: Worm

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

Systems Not Affected: DOS, Linux, Macintosh, Novell Netware, OS/2, UNIX, Windows 3.x

CVE References: CVE-2001-0154

Payload: This worm infects executables, by creating a hidden copy of the original host file, and then by overwriting the original file with itself The hidden copy is encrypted, but contains no viral data The name of the hidden file is the same as the original file, but with a random extension

Large scale e-mailing: This worm searches the Windows address book, the ICQ database, and local files for email addresses The worm sends an email message to these addresses with itself as an attachment

Releases confidential info: The worm randomly chooses a file from the machine to send with the worm to recipients So, the files with the extensions: ".mp8," ".txt," ".htm," ".html," ".wab," ".asp," ".doc," ".rtf," ".xls," ".jpg," ".cpp," ".pas," ".mpg," ".mpeg," ".bak," ".mp3," or ".pdf" would be attached to the email messages with the viral attachment

Distribution

Subject of email: Random

Name of attachment: Random

When this worm is executed, it does the following:

Copies itself to \%System%\Wink<random characters>.exe.

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Note: %System% is a variable The worm locates the Windows System folder (by default, this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.

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Adds the value:

Wink<random characters> %System%\Wink<random characters>.exe

to the registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

or, it creates the registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Wink[random characters]

and inserts a value in this subkey, so that the worm executes when you start Windows.

Attempts to disable on-access virus scanners and some previously distributed worms (such as W32.Nimda and CodeRed), by stopping any active processes The worm removes the startup registry keys, which antivirus products use, and deletes the checksum database files, including:

Anti-Vir.dat

Chklist.dat

Chklist.ms

Chklist.cps

Chklist.tav

Ivb.ntz

Smartchk.ms

Smartchk.cps

Avgqt.dat

Aguard.dat

Copying local and network drives

The worm copies itself to the local, mapped, and network drives as:

A random file name with a double extension; for example, Filename.txt.exe

A .rar archive with a double extension; for example, Filename.txt.rar.

Email

This worm searches the Windows address book, the ICQ database, and local files for email addresses It sends an email message to these addresses with itself as an attachment The worm contains its own SMTP engine and attempts to guess at the available SMTP servers

For example, if the worm encounters the address, [email protected], it attempts to send email via the server, smtp.abc123.com.

The subject line, message bodies, and attachment filenames are random The From address is randomly chosen from email addresses that the worm finds on an infected computer.

The worm will the search files with the following extensions for the email addresses:

mp8

.exe

.scr

.pif

.bat

.txt

.htm

.html

.wab

.asp

.doc

.rtf

.xls

.jpg

.cpp

.pas

.mpg

.mpeg

.bak

.mp3

.pdf

In addition to the worm attachment, the worm may also attach a random file from the computer The file will have one of the following extensions:

mp8

.txt

.htm

.html

.wab

.asp

.doc

.rtf

.xls

.jpg

.cpp

.pas

.mpg

.mpeg

.bak

.mp3

.pdf

As a result, the email message would have two attachments, the first being the worm and the second being the randomly selected file.

"Random" strings comprise the email message that this worms sends The subject can be one of the following:

Worm Klez.E immunity

Undeliverable mail--"[Random word]"

Returned mail--"[Random word]"

a [Random word] [Random word] game

a [Random word] [Random word] tool

a [Random word] [Random word] website

a [Random word] [Random word] patch

[Random word] removal tools

how are you

let's be friends

darling

so cool a flash,enjoy it

your password

honey

some questions

please try again

welcome to my hometown

the Garden of Eden

introduction on ADSL

meeting notice

questionnaire

congratulations

sos!

japanese girl VS playboy

look,my beautiful girl friend

eager to see you

spice girls' vocal concert

japanese lass' sexy pictures

The random word is one of the following:

new

funny

nice

humour

excite

good

powful

WinXP

IE 6.0

W32.Elkern

W32.Klez.E

Symantec

Mcafee

F-Secure

Sophos

Trendmicro

Kaspersky

The body of the email message is random.

Email spoofing

This worm often uses a technique called "spoofing." When the worm performs its email routine, it can use a randomly chosen address it finds on an infected computer as the "From:" address Numerous cases have been reported in which users of uninfected computers received complaints that they sent an infected message to someone else.

For example, Linda Anderson is using a computer infected with W32.Klez.H@mm Linda is not using an antivirus program or does not have the current virus definitions When W32.Klez.H@mm performs its emailing routine, it finds the email address of Harold Logan The worm inserts Harold's email address into the "From:" portion of an infected message, which the worm then sends to Janet Bishop Then, Janet contacts Harold and complains that he sent her an infected message, but when Harold scans his computer, Norton AntiVirus (NAV) does not find anything because his computer is not infected.

If you are using a current version of Norton AntiVirus, have the most recent virus definitions, and a full system scan with Norton AntiVirus, which is set to scan all the files, does not find anything, be assured that your computer is not infected with this worm.

There have been several reports that, in some cases, if you receive a message that the virus has sent using its own SMTP engine, the message appears to be a "postmaster bounce message" from your own domain For example, if your email address is [email protected], you could receive a message that appears to be from [email protected], indicating that you attempted to send an email and the attempt failed If this is the false message sent by the virus, the attachment includes the virus itself Of course, such attachments should not be opened.

The message may be disguised as an immunity tool One version of this false message is:

Klez.E is the most common world-wide spreading worm It's very dangerous by corrupting your files Because of its very smart stealth and anti-anti-virus technic,most common AV software can't detect or clean it.We developed this free immunity tool to defeat the malicious virus You only need to run this tool once,and then Klez will never come into your PC.

NOTE: Because this tool acts as a fake Klez to fool the real worm,some AV monitor maybe cry when you run it If so,Ignore the warning,and select 'continue' If you have any question,please mail to me

If the message is opened in an unpatched version of Microsoft Outlook or Outlook Express, the attachment may be automatically executed Information about this vulnerability and a patch are available at: http://www.microsoft.com/technet/security/bulletin/MS01-020.asp

Virus Insertion

This worm inserts the W32.Elkern.4926 virus as a file, with a random name in the \%Program Files% folder, and then executes it.

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Note: %Program Files% is a variable The worm locates the \Program Files folder (by default, this is C:\Program Files) and copies the virus to that location

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Symantec Security Response offers these suggestions on how to configure Symantec products in order to minimize your exposure to this threat.

Norton AntiVirus for Gateways (SMTP)

Block incoming attachments with .bat, .exe, .pif, and .scr extensions

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

Turn off and remove unneeded services By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server These services are avenues of attack If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates

If a blended 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

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

Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files

Isolate infected computers quickly to prevent further compromising your organization 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

Removal using the removal tool

Symantec has provided a tool to remove the infections of all the known variants of W32.Klez and W32.ElKern Try this removal tool first, as it is the easiest way to remove the threats.

Note on W32.Klez.gen@mm detections

W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez Computers infected with W32.Klez.gen@mm have most likely been exposed to either W32.Klez.E@mm or W32.Klez.H@mm If your computer is detected as infected with W32.Klez.gen@mm, download and run the tool In most cases, the tool will be able to remove the infection.

Manual removal procedure for Windows 95/98/Me

If W32.Klez.H@mm has activated, in most cases you will not be able to start Norton AntiVirus Once this worm has executed, it can be difficult and time consuming to remove The procedure you are to use to manually remove the worm varies with the operating system

Perform the following instructions for your operating system in the order shown below Do not skip any steps This procedure has been tested and will work in most cases.

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Note: Due to the damage that this worm can do, and depending on the number of times the worm executes, the process may not work in all the cases If the process does not work, you may need to obtain the services of a computer consultant.

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1 Disabling System Restore (Windows Me)

If you are running Windows Me, 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 "How to disable or enable Windows Me System Restore"

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

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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 Downloading virus definitions

Download the definitions using the Intelligent Updater Save the file to the Windows desktop This first step is required to make sure that you have the current definitions available later in the removal process The Intelligent Updater virus definitions are available at: http://securityresponse.symantec.com/avcenter/defs.download.html.

For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, read the document, "How to update virus definition files using the Intelligent Updater."

3 Restarting the computer in Safe mode or VGA mode

For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode For instructions on restarting in Safe mode, refer to the document, "How to start the computer in Safe Mode."

For Windows NT 4 users, restart the computer in VGA mode

4 Editing the registry

You must edit the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\Run and remove the wink???.exe value, after you write down the exact name of the wink file.

CAUTION: We strongly recommend that you back up the system registry before making any changes Incorrect changes to the registry could result in permanent data loss or corrupted files Make sure to modify the specified keys only Refer to the document, "How to back up the Windows registry," before you proceed.

Click Start, and then click Run (The Run dialog box appears.)

Type regedit, and then click OK (The Registry Editor opens.)

Navigate to the following key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

In the right pane, look for the following values:

Wink[random characters] %System%\Wink[random characters].exe

WQK %System%\Wqk.exe

Write down the exact filename of the Wink[random characters].exe file

Delete the Wink[random characters] value and the WQK value, if it exists

Navigate to and expand the following key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services

In the left pane, under the \Services key, look for the following subkey:

\Wink[random characters]

and delete it, if it exists.

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Note: This probably will not exist on Windows 95/98/Me-based computers, but check for it anyway.

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Click Registry, and then click Exit.

5 Configuring Windows to show all files

Start Windows Explorer

Click the View menu (Windows 95/98) or the Tools menu (Windows Me), and then click Options or "Folder options."

Click the View tab

Uncheck "Hide file extensions for known file types."

Do one of the following:

Windows 95: Click "Show all files."

Windows 98: In the Advanced settings box, under the "Hidden files" folder, click Show all files

Windows Me: Uncheck "Hide protected operating system files," and under the "Hidden files" folder, click "Show hidden files and folders."

Click Yes if you see a Warning dialog box

Click Apply, and then click OK.

6 Deleting the actual Wink[random characters] file

Using Windows Explorer, open the C:\Windows\System folder and locate the Wink[random characters].exe file (Depending on your system settings, the .exe extension may not be displayed.)

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Note: If you have Windows installed to a location other than C:\Windows, make the appropriate substitution.

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7 Emptying the Recycle Bin

Right-click the Recycle Bin on the Windows desktop, and then click Empty Recycle Bin.

8 Running the Intelligent Updater

Double-click the file that you downloaded in step 1 Click Yes or OK if prompted.

9 Restarting the computer

Shut down the computer, and then turn off the power Wait 30 seconds, and then restart it.

CAUTION: This step is crucial, as re-infection will occur if you skip this step

Allow the computer to normally start If any files are detected as infected with W32.Klez.H@mm or W32.Klez.gen@mm, quarantine them You may find some files, such as Luall.exe, Rescue32.exe, and Nmain.exe.

10 Scanning with Norton AntiVirus (NAV) from a command line

Because the worm damaged some NAV files, scan from a command line.

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Note: These instructions are only for Consumer versions of NAV The Navw32.exe file is not part of the Enterprise versions of NAV, such as NAVCE The NAVCE command-line scanner, Vpscan.exe, will not remove the worm.

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Click Start, and then click Run

Type, or copy and paste, the following:

NAVW32.EXE /L /VISIBLE

and then click OK.

Allow the scan to run Quarantine any additional files that are detected.

11 Restarting the computer

Allow the computer to normally start.

12 Re-installing NAV

NOTE: If you are using NAV 2002 on Windows XP, re-installation may not be possible on all the systems Though, you can try the following:

Open the Control Panel

Double-click Administrative Tools

Double-click Services

In the list, select the Windows Installer Click Action, and then click Start.

To re-install NAV, follow the instructions in the document, "How to restore Norton AntiVirus after removing a virus."

13 Restarting the computer and rescanning

Shut down the computer and turn off the power Wait 30 seconds, and then restart it.

CAUTION: This step is crucial, as re-infection will occur if you skip this step.

Run LiveUpdate and download the most current virus definitions

Start Norton AntiVirus (NAV) and make sure that NAV is configured to scan all the files For instructions, read the document "How to configure Norton AntiVirus to scan all files."

Run a full system scan Quarantine any files detected as infected with W32.Klez.H@mm or W32.Klez.gen@mm.

Manual removal procedure for Windows 2000/XP

1 Disabling System Restore

If you are running 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 "How to turn off or turn on Windows XP System Restore"

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

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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 Downloading virus definitions

Download the definitions using the Intelligent Updater Save the file to the Windows desktop This first step is required to make sure that you have the current definitions available later in the removal process The Intelligent Updater virus definitions are available at: http://securityresponse.symantec.com/avcenter/defs.download.html.

For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, read the document, "How to update virus definition files using the Intelligent Updater."

this is very useful information to you just incase this happens again.

About the author

Posted by cristina of Katharine Gibbs School - New York on January 4, 2005

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