W32.Klez.gen@mm

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Discovered: November 09, 2001
Updated: February 13, 2007 11:39:22 AM
Also Known As: W32/Klez.e@MM, W32/Klez.h@MM, W32/Klez.gen@MM, WORM_KLEZ.E, WORM_KLEZ.G, I-Worm.Klez.e, I-Worm.Klez.h, W32/Klez-E, W32/Klez-G, W32/Klez-H
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154



W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez.

In response to an increased number of variants of W32.Klez@mm, the generic detection, W32.Klez.gen@mm, was created. It was initially released with the definitions released on November 9, 2001.

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

To view an online demonstration on how to download and run this and several other tools, click here .




As aforementioned, in response to an increased number of variants of W32.Klez@mm, the generic detection, W32.Klez.gen@mm, was created. It was initially released with the definitions released on November 9, 2001. This generic detection method has been improved upon and updated several times since then. And, it now includes the .E and .H variants. Specific information about the W32.Klez.E@mm and W32.Klez.H@mm variants can be found at W32.Klez.E@mm and W32.Klez.H@mm , respectively.

For information about how Klez affects a Macintosh, refer to the document, "Are Macintoshes affected by the Klez virus? "

Antivirus Protection Dates

  • Initial Rapid Release version November 09, 2001
  • Latest Rapid Release version September 14, 2017 revision 021
  • Initial Daily Certified version November 09, 2001
  • Latest Daily Certified version September 15, 2017 revision 003
  • Initial Weekly Certified release date November 09, 2001

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

Writeup By: Douglas Knowles

Discovered: November 09, 2001
Updated: February 13, 2007 11:39:22 AM
Also Known As: W32/Klez.e@MM, W32/Klez.h@MM, W32/Klez.gen@MM, WORM_KLEZ.E, WORM_KLEZ.G, I-Worm.Klez.e, I-Worm.Klez.h, W32/Klez-E, W32/Klez-G, W32/Klez-H
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154


W32.Klez.gen@mm is a mass-mailing worm that searches the Windows address book for email addresses and sends messages to all the recipients that it finds. The worm uses its own SMTP engine to send the messages.

The subject and attachment name of the incoming emails are randomly chosen. The attachment will have one of the extensions: .bat, .exe, .pif, or .scr.

The worm exploits a vulnerability in Microsoft Outlook and Outlook Express to try execute itself when you open or preview the message. Information and a patch for the vulnerability can be found at:

http://www.microsoft.com/technet/security/bulletin/MS01-020.asp.
W32.Klez.gen@mm attempts to copy itself to all the network-shared drives that it finds.

Depending on the variant of the worm, it will drop one of the following viruses: which then infects the system.

Email spoofing
Some variants of this worm use a technique known as "spoofing" by which the worm randomly selects an address it finds on an infected computer. The worm uses this address as the "From" address when it performs its mass-mailing routine. Numerous cases have been reported in which users of uninfected computers received complaints that they sent an infected message to another individual.

For example, Linda Anderson is using a computer infected with W32.Klez.E@mm. Linda is neither using an antivirus program nor has the current virus definitions. When W32.Klez.gen@mm performs its email 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 it then sends to Janet Bishop. Then, Janet contacts Harold and complains that he sent her an infected message; however, when Harold scans his computer, Norton AntiVirus does not find anything, because his computer is not infected.

If you are using a current version of Norton AntiVirus and you 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, your computer is not infected with this worm.

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: Douglas Knowles

Discovered: November 09, 2001
Updated: February 13, 2007 11:39:22 AM
Also Known As: W32/Klez.e@MM, W32/Klez.h@MM, W32/Klez.gen@MM, WORM_KLEZ.E, WORM_KLEZ.G, I-Worm.Klez.e, I-Worm.Klez.h, W32/Klez-E, W32/Klez-G, W32/Klez-H
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154



Using the removal tool
Symantec Security Response has developed a tool to remove all the known infections of W32.Klez and W32.ElKern. Click here to obtain the tool. Try this tool first, as it is the easiest way to remove the threats.

Because 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, then download and run the tool. In most cases, the tool will be able to remove the infection.

To view an online demonstration on how to download and run this and several other tools, click here .

If you cannot obtain the tool, then follow the removal instructions in W32.Klez.E@mm or W32.Klez.H@mm .

NOTE: If you are using Norton AntiVirus (NAV) 2000/2001/2002, then in most cases, after you remove the virus, you must re-install NAV. For instructions on how to do this, read the document, "How to restore Norton AntiVirus after removing a virus ."

Writeup By: Douglas Knowles