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11 February 2002
13 February 2007

VBS.Onnet is a VBScript worm that is designed to sent itself to others over an IRC chat client connection.

Antivirus Protection Dates

  • Initial Rapid Release version 12 February 2002
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 12 February 2002
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date pending
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

VBS.Onnet is an encoded VBScript. The script of the worm contains instructions to copy itself onto the hard drive of the infected computer as a random file name with a .vbe extension. The worm then modifies a configuration file, which allows it to send a copy of itself to others over IRC.

The name Sonnet is included in the source code.


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.

NOTE: Virus definitions that can detect and remove VBS.Onnet are included in virus definitions dated February 12, 2002. The instructions that follow assume that you are performing this removal on or after the date that these definitions have been released. To provide information about new threats as quickly as possible, in some cases virus writeups are published before the definitions are released to the public.

If you suspect that the computer is infected with VBS.Onnet, but it has not been detected by Norton AntiVirus, submit the suspect file or files to Symantec Security Response using Scan and Deliver. See the document How to submit a file to Symantec Security Response using Scan and Deliver . If Symantec Security Response determines that the file is infected by a threat for which definitions have not yet been released, you may receive a file by return email that contains "beta" definitions for the threat. Detach and execute the file to install the updated definitions, and then continue with the following instructions.
  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  3. Run a full system scan.
  4. Delete all files that are detected as VBS.Onnet.

Writeup By: Patrick Nolan