Such methods include DRM, CD-checks, Dummy Files, illegal tables of contents, over-sizing or over-burning the CD, physical errors and bad sectors.
Many protection schemes rely on breaking compliance with CD and DVD standards, leading to playback problems on some devices.
Protection schemes rely on distinctive features that: Most CD-ROMs use the ISO9660 file system to organize the available storage space for use by a computer or player.
Most software trying to copy protected media will skip intervals of sectors when confronted with unreadable ones, expecting them all to be bad.
In contrast to the original approach, the protection scheme expects the sectors to be readable, supposing the medium to be a copy when read-errors occur.
This was designed for Audio-CDs (which for a few years were the only CDs), where this information is used to keep the drive on track; nevertheless the Q-channel is filled even on Data-CDs.
A protected program can check whether the CD-ROM is original by positioning the drive behind sector 6553 and then reading from it — expecting the Mary version to appear.
Data Position Measurement (DPM) detects these little physical differences to efficiently protect against duplicates.
[citation needed] The Red Book CD-DA audio specification does not include any copy protection mechanism other than a simple anti-copy flag.
Starting in early 2002, attempts were made by record companies to market "copy-protected" non-standard compact discs.
Also, many ordinary CD audio players (e.g. in car radios) had problems playing copy-protected media, mostly because they used hardware and firmware components also used in CD-ROM drives.
[1] Upon inserting such a disc in the CD drive of a computer running Microsoft Windows, the XCP software would be installed.
Several publishers of antivirus and anti-spyware software updated their products to detect and remove XCP if found, on the grounds that it is a trojan horse or other malware; and an assistant secretary for the United States' Department of Homeland Security chastised companies that would cause security holes on customers' computers, reminding the companies that they do not own the computers.