W32.HLLW.Yodo.B is a mass-mailing worm that sends itself through any MAPI-compliant email client, including Microsoft Outlook.
The mail has the following characteristics:
Subject: A E-card just for you from your friend
Message: Hello. I just wanted to send you this e-card to show you how much of a friend you are to me! Please look at the attached E-card.
Scanned with Norton Anti-Virus
Attachment: ecard.exe
Type: Worm
Infection Length: 73,728
Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP
Systems Not Affected: Linux, Macintosh, OS/2, UNIX
Virus Definitions (Intelligent Updater) *
August 25, 2003
Virus Definitions (LiveUpdate™) **
August 27, 2003
*
Intelligent Updater definitions are released daily, but require manual download and installation.
Click here to download manually.
**
LiveUpdate virus definitions are usually released every Wednesday.
Click here for instructions on using LiveUpdate.
Wild:
Number of infections: 0 - 49
Number of sites: 0 - 2
Geographical distribution: Low
Threat containment: Easy
Removal: Easy
Threat Metrics
Wild:
Low
Damage:
Low
Distribution:
Low
Distribution
Subject of email: A E-card just for you from your friend
Name of attachment: ecard.exe
Size of attachment: 73,728
When W32.HLLW.Yodo.B runs, it performs the following actions:
Displays the following message:
Copies itself as the following:
%Windir%\ecard.exe.
%System%\ecard.exe
NOTES:
%Windir% is a variable. The worm locates the Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.
%System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
Adds a value:
"E-Card"="ecard.exe"
to the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
so that the worm runs when Windows starts.
Deletes the following files:
%Windir%\*.ini
%System%\regedt32.exe
Sends itself through any MAPI-compliant email client, including Microsoft Outlook.
The mail has the following characteristics:
Subject: A E-card just for you from your friend
Message: Hello. I just wanted to send you this e-card to show you how much of a friend you are to me! Please look at the attached E-card.
Scanned with Norton Anti-Virus
Attachment: ecard.exe
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.
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.HLLW.Yodo.B.
Delete the value that was added to the registry.
Restore the files that the worm deleted.
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:
"How to disable or enable Windows Me System Restore"
"How to turn off or turn on Windows XP System Restore"
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.