Digital Rights Management, or DRM, is a technology that divides opinion.
For some campaigners, it is "defective" software that cripples products and should be abolished immediately.
To the record and film industry it is a "crucial" tool that allows them to protect and sell their goods online.
As a result, the software locks have become the focus of a game of digital cat and mouse. As each new or updated DRM system is released an army of hackers pores over the code and often releases a workaround within hours or days.
For example, in August 2006 a hacker managed to circumvent the Microsoft Windows DRM system within three days of the software giant releasing an update intended to block previous workarounds.
In July this year, updates intended to protect tracks sold through Microsoft's Zune Marketplace were also cracked, whilst Apple's Fairplay DRM system has come under similar scrutiny
"DRM is seen as fair game in the same way as firewalls are for hackers," said analyst Mark Mulligan of JupiterResearch.
However, not all DRMs are equal. Music was more likely to be targeted by hackers and critics because of people's expectations, said Mr Mulligan.
"One of the big failings of DRM [on music downloads] is the complete contradiction in ideology behind selling music in CD format versus selling music in digital format," he explained.
Most CDs do not have any form of DRM and so almost all of the content is already available DRM-free, he said. Therefore any hacks of music DRM systems were done "just for fun".
Some music retailers have started to test the waters by selling downloads DRM-free.
In April this year, music giant EMI announced that it would sell "premium" music downloads through Apple's iTunes without the locks, whilst earlier this month Vivendi's Universal Music announced a similar deal as part of a six month trial.
But the vast majority of music downloads are still sold with DRM. The record industry says this is for two reasons.
"One is to enable different business models at different price points," said Richard Gooch, director of technology at the International Federation of the Phonographic Industries (IFPI) "The other is to protect against piracy."
Mr Gooch pointed to services such as Napster that offer a subscription service with access to more than 4 million tunes.
"Those services which give you access to everything for a fixed period of time - it's difficult to see how that type of a service could be offered if it wasn't operated with DRM," he said.
"You can't send a user an e-mail saying - 'by the way, those 4 million tracks I gave you, you wouldn't mind deleting them would you?'."
DRM does the job for Napster by making tracks unplayable at the end of the subscription period.
Similar technology is used to control movie downloads as part of services such as CinemaNow and Amazon's Unbox service.
Mr Mulligan says that DRM on DVDs does not attract the same level of mirth from the digital community as it does for music downloads.
"There isn't a contradiction of approach between the physical and digital products," said Mr Mulligan.
"Video content and DVD has always been very protected - people do not expect to copy DVDs easily," he said.
Apple boss Steve Jobs made a similar observation earlier this year in an open letter posted on the company's website.
"The music and video markets are not parallel. The video industry does not deliver 90% of its content DRM-free," he wrote, referring to CDs. Other groups such as the Motion Picture Association of America (MPAA) also agree.
However, DRM for movies does still attract attention from the hacking community.
For example, the Advanced Access Content System (AACS) used on next-generation HD DVD and Blu-ray discs was cracked six months after it hit shelves. Other cracks appeared soon after.
Although this had led to some people sharing movie files illegally on the web it is not at the same level as for music.
"There is some demand for it but it is a very different scenario than for CDs," he said.
Another potential target for hackers is the burgeoning sector of on-demand television.
But like with film, Mr Mulligan believes it will not be hit as hard as the DRM used for music.
"DRM is better suited to television content because it fits with demand as well as expectations," said Mr Mulligan.
In particular, he said, people were unlikely to want to keep much of the ephemeral content available on television such as news or soap operas.
Some TV companies also seem sanguine.
The Microsoft DRM system used by the BBC's iPlayer has already been cracked and people using the trial version of the player have already been able to strip programmes of their DRM.
At its launch, Ashley Highfield, director of future media and technology at the BBC admitted: "Piracy is always going to happen."
It is a view shared by Mr Mulligan
"The bottom line is there will never be a watertight digital rights management solution" he said.
The view is disputed by people within the movie and music industry.
"DRM is not going away," said Mr Gooch.
And so until one side wins out, the game of cat and mouse will continue.