The suit filed in Seattle last week alleges that the tool violates spyware legislation and consumer rights in California and Washington. It is seeking unspecified damages as well as class action status.
Windows Genuine Advantage collects information about a system's configuration including make and model, regional settings, product keys, a Global Unique Identifier, the name and revision number of the system's Bios and hard drive serial number.
The tool periodically checks in with a Microsoft server to verify that the software was obtained legally.
The lawsuit charges that Microsoft misled consumers about the tool's purpose by bundling it with a batch of security updates.
"The updates from Windows Automatic Update installed WGA 2006 Verification without specific notice to or approval from the users, even when the users sought to specifically control what was installed on their system through the Custom installation setting," the legal complaint stated.
Microsoft distributed a revision to the tool on 24 April that was labelled as a 'high priority update'. The download was released on the same day as a number of security updates.
The updated version presented users of pirated copies of Windows with periodic warnings. It also contacted a Microsoft server on a daily basis or whenever a user booted up the system.
The daily check-in prompted users to complain that Windows Genuine Advantage is essentially spyware.
Microsoft initially changed the tool to check in every 14 days. Last week the company released instructions on how to remove Windows Genuine Advantage and changed it to contact the server only when the tool is updated.
The tool is optional, although Microsoft requires users to pass WGA authentication for free downloads and non-security patches.
The software vendor has always said that security updates will be made available to all users to prevent large scale worm outbreaks that use known Windows vulnerabilities.
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