W32.Allgro@mm

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Discovered: August 17, 2001
Updated: February 13, 2007 11:48:25 AM
Also Known As: Win32.All3-gro.A@mm
Type: Worm


W32.Allgro@mm is a mass-mailing worm that is written in C++. The worm appears as an email message with the following characteristics:

Subject: New antivirus tool
Message: Hey, checkout this new antivirus tool which checks your system for viruses
Attachment: Antivirus.exe

The worm is disguised as a program that you can use to remove worms and Trojans from your computer.

Antivirus Protection Dates

  • Initial Rapid Release version August 18, 2001
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version August 18, 2001
  • Latest Daily Certified version August 09, 2016 revision 001

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


Technical Description


Upon execution, the worm copies itself as the file %System%\Setup30.exe.

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

It then adds the value

Kernel Setup

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run

so that the worm is executed every time that Windows starts.

The worm propagates by using Messaging Application Processing Interface (MAPI) commands to send email to addresses that are found in email messages that are stored on the infected system.

The worm performs some actions that are designed to be beneficial to the system. It attempts to clean the system of some common worms and Trojans:

  • W32.Sircam.Worm@mm
  • W32.Badtrans.13312@mm
  • PrettyPark.Worm

In addition to these specific worms, it attempts to remove script threats. This is accomplished by deleting all .vbs files and the Mirc.ini and Script.ini files if they are found in specific folders on drive C.

Due to the nature of this worm, it is highly possible that important user data could be deleted.

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.


Removal


To remove the worm, delete all files that are detected as W32.Allgro@mm and remove the registry entry that it added (details follow). Files that were deleted by the worm must be restored from backups.

To remove the worm:

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and run a full system scan. Be sure that NAV is configured to scan all files.
  3. Delete all files that are detected as W32.Allgro@mm.

To edit the registry:

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry can result in permanent data loss or corrupted files. Please make sure you modify only the keys that are specified in this document. For more information about how to back up the registry, please read How to back up the Windows registry before proceeding with the following steps. If you are concerned that you cannot follow these steps correctly, then please do not proceed. Consult a qualified computer technician for more information.
  1. Navigate to and select the following key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\
    Windows\CurrentVersion\Run
  2. In the right pane, look for and select the value

    Kernel Setup
  3. Press Delete, and then click Yes to confirm.
  4. Exit the Registry Editor.


Writeup By: Peter Szor