Controversial copy-protection mechanisms on CDs could be negated with something as simple as a marker pen.

According to one German geek who sent the tip to technical magazine Chip.de, a variety of copy-protection systems, including Cactus Data Shield and KeyAudio, which also stop music CDs being played in CDRom drives, can be circumvented with a felt-tip pen.

Copy-protection systems work by adding a corrupt data track to the outside edge of a CD. This track is ignored by common audio CD players but prevents copying, and sometimes playing, in the more sensitive PC CD drives.

By covering up a portion of the dividing line and outside track on the CD, without touching the last audio track, it is possible to fool the CD player into thinking that the extra corrupt data track does not exist. The marker pen line can easily be wiped away afterwards with a soft cloth.

A similar result was also obtained by sticking bits of a Post-It note along the edge of the CD, but this is not advised as the paper may come loose and damage the drive.

A number of artists have come under fire from fans for releasing CDs with copy-protection systems. Recently, Michael Jackson, Celine Dion, Natalie Imbruglia and Eminem have all taken some flak for releasing CDs that do not play in PC CD drives.

The record industry has backed such systems as a way of cutting back on the trade of illegal MP3s, but even industry giant Philips, which co-created the CD format, has condemned its usage as damaging.

It's probably only a matter of time before a new system, not so easily avoided, becomes commonplace in preventing users making a backup of music they have bought, but until then it seems all you need is a steady hand.