Sony BMG is facing three lawsuits over its controversial anti-piracy software.
A CD by Celine Dion is protected with the anti-piracy system
Revealed in late October by Windows expert Mark Russinovich, the software copy protection system hides using virus-like techniques.
One class-action lawsuit has already been filed in California and another is expected in New York.
Digital rights group, the Electronic Frontier Foundation (EFF), is also gathering information from users to see if a case can be brought.
The row erupted following Mark Russinovich's discovery that Sony BMG in America was using a so-called "root kit" to conceal the program used to stop some of its CDs being copied.
"Root kits" are being increasingly used by virus makers to hide their malicious wares deep inside the Windows operating system.
Sony BMG used a program called XCP created by UK firm First 4 Internet that employed similar cloaking systems to hide the proprietary media player used to play tracks on 20 CDs made by the music giant and sold in the US.
But since Dr Russinovich wrote about his discovery the row has snowballed and now has led to lawsuits being filed against Sony BMG.
One filed in Los Angeles by Californian attorney Alan Himmelfarb wants to stop Sony BMG selling more CDs protected by anti-copying software and seeks damages for Californians that have bought any albums protected this way.
XCP PROTECTED CDS
Trey Anastasio - Shine
Celine Dion - On ne Change Pas
Neil Diamond - 12 Songs
Our Lady Peace - Healthy in Paranoid Times
Chris Botti - To Love Again
Van Zant - Get Right with the Man
Switchfoot - Nothing is Sound
The Coral - The Invisible Invasion
Acceptance - Phantoms
Susie Suh - Susie Suh
Amerie - Touch
Life of Agony - Broken Valley
Horace Silver Quintet - Silver's Blue
Gerry Mulligan - Jeru
Dexter Gordon - Manhattan Symphonie
The Bad Plus - Suspicious Activity
The Dead 60s - The Dead 60s
Dion - The Essential Dion
Natasha Bedingfield - Unwritten
Ricky Martin - Life
According to a report in the Washington Post the lawsuit alleges that Sony BMG has broken three Californian laws. At the same time New York lawyer Scott Kamber is planning a class-action lawsuit for all Americans affected.
The EFF is also gathering stories from buyers of Sony BMG CDs protected with XCP. In a statement the organisation said: "We're considering whether the effect on the public, or on EFF members, is sufficiently serious to merit a lawsuit".
At the same time the Italian digital rights group, Electronic Frontiers Italy, has asked the nation's government to investigate Sony over its use of anti-piracy software.
A weblog documenting the unfolding controversy and calling for a boycott of Sony products has also been created.
When contacted a representative for Sony BMG in the UK referred all calls to its corporate headquarters in New York. A call to a spokesman in that office has yet to be returned.
The EFF also released a partial list of all the CDs protected with XCP. The list includes popular artists such as Natasha Bedingfield, Celine Dion and Amerie. It also gave advice for ways to spot if a CD is XCP protected.
So far Sony BMG has not released a list of how many CDs are protected or how many have been sold. It has only said that "about 20" titles are protected with the controversial program.
However, the row does not appear to be denting interest in one of the CDs protected by XCP because at the time of writing Neil Diamond's 12 Songs album was the top seller on the Amazon.com website.
Anti-virus companies are starting to release software that can spot the XCP files. Symantec said it had made tools that can find the files but will not remove them.
Computer Associates said that it would be releasing a tool to completely uninstall the XCP program.
At the same time anti-virus firm Kaspersky Labs branded the XCP program spyware because it hides itself, could compromise security and can slow machines down.
Dr Russinovich has continued his investigation of the XCP software and has confirmed that when installed it can make a Windows computer more unreliable.
He also criticised Sony BMG for making it difficult to get hold of software that can uninstall XCP.