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Copy protection involves technological barriers which either prevent electronic content from being copied or make the task more difficult. The techniques used have developed along with technology, most notably the growth of digital content. Some systems have caused controversy, as users believe they unfairly restrict what may be seen as legitimate usage.
The first popular form of copy protection was Macrovision. This was a system used to prevent copying of video cassettes. It took advantage of the fact that some of the lines used to transmit a television signal do not appear on the screen itself. By inserting a specially coded signal in these lines, the protection meant that any copies had badly distorted pictures. Most DVD recorders are set up to stop recording if they detect a Macrovision signal from a video recorder connected to them.
When video cassettes were replaced by DVDs, the threat of illegal copying increased. This isbecause the content is stored digitally, making it possible to make an exact copy without any loss of quality. It’s also possible to copy digital content as quickly as a computer can process the information, rather than having to play the content in real time. The DVD industry uses a form of copy protection known as CSS, which stands for Content Scramble System. This locks the content so it can only be played using keys which can be read by DVD players, but are stored in an area of the disk which is not copied by computers.
While there are several computer programs which can overcome the restrictions of CSS, they are illegal in many countries. In the United States, they are covered by the Digital Millennium Copyright Act. This bans any software which bypasses digital copy protection. Many such programs are available from websites based in countries with looser copyright laws. Real Networks attempted to launch what it billed as a legal DVD copying program in 2008, though as of April 2009 it was banned by a court pending a civil trial.
Copy protection itself is not as popular in digital audio content, though some commercial CDs include technology to prevent copying. The more common anti-piracy technique for downloadable music files is digital rights management. This encodes the relevant files so that they only play on a particular computer or portable device, though some systems allow the song to play on a fixed number of devices. This system has caused controversy as some users believe that once they buy digital music files, they should be able to play them anywhere, as with a CD. There are also claims that digital rights management unfairly restricts listeners to using particular audio programs or music players produced by particular manufacturers.
With computer software, copy protection doesn’t usually involve literally preventing files from being copied. Instead, there are a range of techniques designed to stop the copied version being used. In some cases these can involve supplying a dedicated user name and license number to legitimate customers. Other techniques involve the user having to activate the software before it will work fully, usually by connecting to the manufacturer via the internet so that the file can be checked and verified as legitimate.