Alert level

Trojan:JS/Agent.FA


Encyclopedia entry
Updated: Mar 27, 2008  |  Published: Aug 08, 2007

Aliases
  • Trojan-Downloader.JS.IstBar.ax (Kaspersky)
  • VBS/IstBar (AhnLab)
  • JS/ForcePopup (Authentium (Command))
  • Trojan.Clicker.CM (BitDefender)

Alert Level (?)
High

Antimalware protection details
Microsoft recommends that you download the latest definitions to get protected.
Detection initially created:
Definition: 1.45.287.0
Released: Oct 07, 2008

Summary

Trojan:JS/Agent.FA is malicious Javascript embedded in a Web page. The Javascript is designed to circumvent popup blocking by security applications.

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Symptoms

The presence of one or more popup windows that bypass installed popup blockers may be indicative of a Web page hosting Trojan:JS/Agent.FA.

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Technical Information (Analysis)

Trojan:JS/Agent.FA is malicious Javascript embedded in a Web page. The Javascript is designed to circumvent popup blocking by security applications, including popup blockers from Google Toolbar, Internet Explorer, and Norton Internet Security. The malicious popup could allow site redirection which could lead to possible downloading and executing of further malicious files.

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Prevention

Take the following steps to help prevent infection on your system:
  • Enable a firewall on your computer.
  • Get the latest computer updates.
  • Use up-to-date antivirus software.
  • Use caution with attachments and file transfers.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows XP Internet Connection Firewall.
To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Click Change Windows Firewall Settings.
  4. Select On.
  5. Click OK.
To turn on the Windows Firewall in Windows Vista
  1. Click Start, and click Control Panel.
  2. Click Security.
  3. Click Turn Windows Firewall on or off.
  4. Select On.
  5. Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. You can use the Automatic Updates feature in Windows XP to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows XP
  1. Click Start, and click Control Panel. 
  2. Click System.
  3. Click Automatic Updates.
  4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
Use caution with attachments and file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources.  Use extreme caution when accepting file transfers from known or unknown sources.

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Recovery

Trojan:JS/Agent.FA may download and install additional malicious software, thus manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft online scanner (http://safety.live.com). For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.

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