Copy protection

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From the analog copy protection pulses on VHS tapes to the sophisticated encryption and middleware of Discs, the battle against unauthorized copying has been a constant thread throughout the history of data storage. Disc copy protection refers to various methods used to prevent unauthorized copying of data from CDs, DVDs, and other optical discs. These methods aim to protect copyrighted content like software, movies, and music.

DRM icons

Common copy protection measures

Since the era of floppy disks (circa 70s-90s) saw a constant battle between software developers and copy pirates. To protect their valuable software, developers employed various copy protection methods, creating a fascinating game of technological innovation.

70s-90s (On-disk and Off-disk copy protection)

On-disk methods involved manipulating the data on the floppy disk itself to hinder copying:

  • Non-Standard Disk Formats: Software might format the disk in a way incompatible with standard copying programs, requiring specialized tools.
  • Invalid Checksums/CRCs (Cyclic Redundancy Checks): Adding errors to checksums, data verification tools, would cause copied disks to fail integrity checks.
  • Hidden Data: Data essential for the software's operation could be hidden in unused sectors or encoded in special ways, making it difficult for copying software to detect and copy accurately.
  • Bad Sectors: Deliberate introduction of bad sectors on the disk would cause errors during the copy process, leading to incomplete or unusable copies.
  • Index/Offset Data Alignment: Misaligning data sectors or index information could confuse copying software, resulting in garbled data on the copy.
  • Weak/Flaky Bits: Data bits on the disk could be weakened intentionally, causing them to be misread during copying, leading to program instability on the copied disk.

Off-disk methods relied on external factors to prevent unauthorized copying:

  • The Code Wheel: A physical wheel with codes printed on it, included with the software. The program might prompt the user for specific codes from the wheel during installation, preventing copying without the physical wheel.
  • Manuals with Unlock Codes: Unlock codes printed in the software manual were required during installation, making copying without the manual difficult.
  • Copy Protection Software: Separate software programs might be included on the disk, checking for the presence of the original media before allowing installation.
  • Hardware dongles: The data on disk is encrypted, and is decrypted upon runtime using a dongle attached to the computer. Due to its expense, it was usually limited to business software or beta versions (see Shadow Warrior for an example of the latter)

As with any security measure, these copy protection methods eventually faced their match. Skilled programmers developed tools and techniques to bypass these protections, creating "cracks" that allowed users to copy software. This ongoing battle between protection and cracking fueled the innovation in both areas throughout the floppy disk era.

LGR: The History of DRM & Copy Protection in Computer Games
Technology Connections: Macrovision - The Copy Protection in VHS

The rise of digital distribution and more robust security measures eventually rendered floppy disk copy protection obsolete. However, the ingenuity and creativity behind these early methods remain a fascinating chapter in the history of software protection.

2000s

Digital Rights Management (DRM) restricts how a disc's content can be accessed or copied. It may require online activation, limit installations to a certain number of devices, or disable specific features on copied discs. CD-Cops was the first CD-ROM protection system to use the geometry of the CD-ROM media rather than a hidden "mark". See PCGamingWiki: Types of DRM methods on Discs.

  • Middleware: SecuROM is one of the most well-known examples, SecuROM (introduced in 1998) employed a combination of techniques. It used disc encryption, monitored system resources for signs of copying, and sometimes included features like copy limitation or online authentication. LaserLock is a middleware relied on a special authentication layer burned onto the disc itself. During installation, the software would verify the presence of this layer to ensure it was an original disc. SafeDisc is Similar to SecuROM, utilized disc encryption and copy protection features. It was also known for its aggressive copy protection measures, which sometimes caused conflicts with legitimate software or hardware. See PCGamingWiki DRM#Middleware section.
  • CD-checks: Software on the disc searches for specific data patterns or physical characteristics to verify it's an original disc and not a copy.
  • Dummy files: Irrelevant data files are added to the disc to confuse copying software and increase the disc size beyond its standard capacity, making it difficult to copy entirely.
  • Illegal tables of contents: Errors are introduced in the data layout information on the disc, tricking copying software into making an unusable copy.
  • Over-sizing/over-burning: The disc is encoded with more data than its standard capacity allows. This may prevent some copying software from handling it properly.
  • Physical errors and bad sectors: Intentional imperfections are introduced on the disc's surface to prevent reliable reading by copying tools.
Many older software programs and games are unusable today because some of the original copy protection methods relied on activation servers that are no longer operational.
Tech Tangents: Digital Decay Of 2000's PC Game DRM
MVG: SecuROM - The PC CD-ROM DRM that broke games

Physical reliability vs. digital storage

While digital storage boasts superior convenience and accessibility, it relies on proper backups to ensure long-term data integrity. Media failure or file corruption can still lead to data loss. Physical discs, on the other hand, present their own challenges.

1. Access Control and Ownership
Digital Storage: "Despite the convenience of digital storage, ownership of digital media can be ambiguous.[1] Unlike physical copies, digital ownership often grants only a license to access content, not outright ownership.[2] Platforms like Steam, for instance, may have policies restricting access to your digital library after death.[3] In contrast, GOG offers offline installers that cannot be revoked, even if the game developer removes the title from their platform. This means that if you've purchased a game on GOG, you can keep it indefinitely, as long as platform is in business.[4] It is worth noting that GOG modifies game files for compatibility reasons, this results in the elimination of the original game installers, providing only custom setup executables."
Physical Storage: "Physical media provides a sense of tangible ownership, even though some copy protection methods may limit resale and sharing options or even usability. But most of the time you still have greater control over your discs or cartridges compared to digital ownership."
2. Long-Term Preservation
Digital Storage: "Digital storage formats and platforms can become obsolete over time. Reading a floppy disk today is a challenge, and future technology might not be able to access current digital formats. Long-term preservation of digital media requires ongoing migration and maintenance. Although there are several convenient options such as using Network-attached storage (NAS) or cloud service providers for your digital storage and preservation. Choosing the correct steps for ripping and compression methods is crucial for preservation though."
Physical Storage: "Physical media can degrade over time due to disc rot or scratches (e.g., all DVD's issued by Warner Bros from 2006-2008 (including all Warner HD-DVD's) have a defect that makes them rot). Disc rot is a gradual chemical breakdown of the disc's reflective layer, rendering the data unreadable over time and is a concern for long-term data archiving. However, with proper care, physical discs and cartridges can last for decades, making them a more reliable format for long-term archival purposes. The drawback is the significant physical storage space they require."
3. Vulnerability to Loss
Digital Storage: "Digital storage is susceptible to data loss due to server crashes, malware attacks, or accidental deletion. Proper backups are crucial to mitigate this risk."
Physical Storage: "Physical media can be lost, stolen, or damaged through accidents. Fire, floods, or mishandling can destroy your physical collection."
4. Censorship and Availability
Digital Storage: "Digital content can be censored or removed from online platforms by the provider or due to copyright issues. This can lead to the loss of access to previously purchased digital media. Providers may remove content from digital stores due to censorship, copyright issues even after purchase, or simply decide to delist the software entirely.[5][6] Digital content on some platforms like Android can be especially vulnerable to access loss. Unlike other platforms, there's a lack of interest in preserving mobile software, leading many older applications and games to become unavailable over time. Even successfully preserved applications and games with their APKs and associated data files can still face hurdles. Restrictive copy protection methods, like defunct activation check servers, can cause problems. Additionally, MMOs dependent on private servers are only playable if the community revives them."
Physical Storage: "Physical media offers more control over access and censorship. Once you own a physical copy, it cannot be easily removed or altered by a third party."

Bypassing copy protection

This section is for informational purposes only.

Distributors rarely release official patches to bypass activation, updates that remove online activation requirements altogether, if their servers are down. Some software cracks bypass copy protection checks, allowing installation and use of software without the original disc or disk. All types of these modified executables, often called "Crack" for Floppy, "NoCD" for CD-ROMs or "NoDVD" for DVD-ROMs, are distributed on illegal sources. Having said that, there are examples like Tom Clancy's Rainbow Six: Vegas 2 update version 1.03, where it was discovered that Ubisoft's patch solving the locking problem on digital copies due to disc check copy protection was a NoDVD crack taken from Reloaded, a pirated games group, and re-released as an official patch.[1]

On mobile platforms like Android, a large number of older software applications are unusable today due to restrictive copy protection methods. As a result, some users resort to patching the executables to bypass the protection after preserving the files including "APK and Data" files because as mentioned in #Physical reliability vs. digital storage section, even those successfully preserved applications can still face hurdles due to restrictive copy protection methods like defunct activation check servers.

For preserving and bypasing off-disk copy protection like code wheels, simulators (e.g., the oldgames.sk code wheel simulator) are more practical than static scans because they replicate the device's functionality as well.

Download-required and online-dependent discs

While some of these do not directly related to disc copy protection;

  • Some MMO (Massively Multiplayer Online) games distributed on discs (like Aion, Guild Wars, and Overwatch 1) become unplayable once the game servers are shut down. In these cases, the disc itself is useless and retain value only for historical preservation purposes. However some MMOs are unplayable by server shutdown, enthusiasts may create and maintain private game servers to keep the games alive unofficially. See Preservation projects#Private game servers section for revived private game server projects.
  • Some older software discs relies on online access for retro web browsing features and specific websites. If these websites disappear, the disc itself becomes largely useless, retaining value only for historical preservation purposes. However, archived versions of the websites might exist, and in that case, proxy projects can enable you to experience retro web browsing.
  • Some software discs may require obsolete dependencies like older versions of Java, Flash Player, ActiveX, or Shockwave. While these dependencies aren't always essential for the software to function, in some cases, you may need them. If the disc doesn't include them for some reason, you'll need to search the internet for the specific version required to make the software work. For example, in the PC version of "Street Fighter Zero" you'll only need Intel's obsolete specific version of Indeo codec if you want to watch the intro FMV.[7][8]
  • Some discs require downloaded patches and incompatible with offline play (especially for eighth-generation and later consoles). In these cases, the disc itself has limited functionality, retaining value primarily for historical preservation purposes. See DoesItPlay.org for more information about this.
  • As mentioned in #Common copy protection measures, some older software program and game discs are unusable today because of the original copy protection methods relied on activation servers that are no longer operational.

Codec situations and home media discs

To playback (either digital or physical) home media content, you'll need compatible hardware and/or software that supports the codec used by the media. Most of the streaming services uses DRM, for example Netflix uses a multi-DRM strategy, which includes using multiple DRM such as Widevine, Fairplay, and Playready DRM. Physical home media discs, particularly DVDs, HD-DVDs, and Blu-ray discs, are often encrypted. This means that even if you have the disc, you may need to bypass copy protection to create a backup copy. See Home media players#Media player software and ripping pages for more information.

Emulation

  • Daemon Tools can act as emulator for middleware like SecuROM, essentially trick the software into thinking the original protected disc is present, allowing it to run without the actual disc.
  • DiscCheckEmu can bypass copy protection measure that rely on "Disc Checks." Disc Checks involve the software verifying the presence of specific data patterns on the disc. DiscCheckEmu can potentially spoof these checks, deceiving the software.
  • SafeDiscLoader targeting middleware like specific versions of SafeDisc (2.7 to the latest 4.9), might utilize techniques like DLL (Dynamic Link Library) hooking to emulate disc checks or bypass other protection mechanisms employed by that particular middleware version.
  • SafeDiscShim is a compatibility tool that allows for SafeDisc protected games which utilize the insecure Macrovision Security Driver ("secdrv.sys") to run on modern versions of Windows.
  • CDEmu
  • There are some revive projects out there for emulating some of the middleware type protections such as Games for Windows - LIVE.
DOSBox-X issue page: SafeDisc / SecuROM emulation for games

Disc ripping and scan for copy protection

MPF Software and BF2DVD - SafeDisc 3+ detected
Main article: Ripping games

As mentioned on the ripping games page, in most cases, the MPF software (a frontend for various low-level byte-perfect CD dumper utilities) handles disc ripping tasks with ease if you have a compatible optical drive (capable of reading the specific disc). The "Scan for protection" option allows you to check if your disc has copy protection. Verify your disc images against databases like redump.info for accuracy. See disc-based ripping for detailed workflows.

Preserving Copy Protection in Disc Images

Copy protection mechanisms on CDs/DVDs, rely on physical disc characteristics (e.g., Data Position Measurement (DPM), subchannel data, intentional sector errors, or unique disc identifiers) to prevent unauthorized copying. These protections complicate disc ripping, as simple tools cannot capture low-level features like DPM or subchannels, resulting in disc images that fail protection checks. Proper ripping can preserve these mechanisms, creating disc images that run without NoCD/NoDVD executable patches, which is ideal for archival purposes and maintains software authenticity and it prevents the potential harms of NoCD/NoDVD executable patches such as compatibility or security issues. However, this process require specialized hardware and software to capture. Standard ISO files miss these features, rendering images unusable without patches. Formats like MDF/MDS is needed to preserve these protections. For example: 

 - SecuROM (versions 4–6) uses DPM to verify data density variations.
 - SafeDisc embeds intentional errors or digital signatures in sectors, needing subchannel data preservation.
 - StarForce employs complex DPM and driver-based checks, often requiring precise emulation.
 - Tages uses unique disc identifiers, detectable only by specific drive firmware.
 - LaserLock, ProtectCD, CD-Cops manipulate subchannel data or sector layouts, complicating standard ripping.
Data Position Measurement (DPM)
is a CD and DVD copy protection mechanism that operates by measuring the physical location of data on an optical disc. DPM is effective because it exploits the fundamental physical differences between two distinct disc manufacturing methods: replication (pressing/stamping) and duplication (burning). When you decide to manufacture CDs, especially for short runs, you typically face a choice between getting pressed CDs or burned CDs. These are sometimes referred to as replicated discs and duplicated discs, respectively. Understanding the difference in their manufacturing methods clarifies why these terms are used and how DPM works.
  • Replicated Discs (Pressed / Stamped): These are what most people think of as commercial CDs. Manufacturing involves taking a master disc (often a glass master) and using it to create a nickel stamper. Polycarbonate substrates are then pressed against this stamper, physically molding the data (pits and lands) directly into the disc's surface. This process creates an exact, microscopic replication of your original master. The result is a "professional grade" disc with highly precise and consistent physical data positioning across all discs in a production run. DPM expects to find data at these exact, consistent physical locations.
  • Duplicated Discs (Burned / CD-R / DVD-R): This method is akin to what most people do when burning CDs at home. A manufacturer uses the data you submit (often on a CD-R) and burns it onto additional blank, recordable discs (CD-Rs, DVD-Rs) using a laser. These blank discs contain a dye layer that changes state when heated by the laser, creating marks that represent the data. While manufacturers can perform this on a larger scale, the process itself, unlike pressing, inherently introduces subtle physical variations in the exact size, shape, and placement of these burned marks.
DPM detects these subtle physical differences. A genuine, replicated disc will always have its data at the expected, precise physical location, while a burned (duplicated) copy will exhibit minute physical variations that DPM identifies as an unauthorized copy. In concert with emulation software, a recordable media physical signature (RMPS) can be created from captured DPM data, allowing a duplicated disc to appear as an original and bypass the protection. This technique was notably pioneered by Alcohol 120% with its .mds file format.
Hardware Requirements

Optical drives must support low-level reading, such as subchannel data (RAW+Sub96) or DPM. Plextor drives (e.g., PX-760A, PX-755SA) are preferred for their D8 read command and DPM capabilities. Some older ASUS or Lite-On drives may work, but modern USB drives often lack these features, necessitating older, compatible drives. Certain protections (e.g., Tages) may require specific drive firmware. See drive compatibility for details.

Software and File Formats
 - Alcohol 120% (MDF/MDS): Captures DPM and subchannel data, ideal for SecuROM and SafeDisc on DVDs. The MDS file stores metadata.
 - DiscImageCreator (.scm/scram): Captures raw, scrambled CD data, suitable for SafeDisc, LaserLock, or early SecuROM.
 - CloneCD (.ccd/.img/.sub): Stores subchannel data for CD protections (e.g., CD-Cops, ProtectCD) but struggles with DPM-heavy protections.
 - Aaru (.aaruf): A preservation-focused format that captures raw sectors, subchannels, and DPM, though less widely supported.
 - BlindWrite (.bwa/.bwt): Captures subchannel data and some physical characteristics, used for protections like ProtectCD, but much less common than MDF/MDS.
Emulation of the Disc Drive

While the aim is to retain the original copy protection, making the game believe the original disc is present: the virtual/emulated drive is performing "emulation" of the drive itself to deliver the preserved protection data to the game. If the MDF/MDS image is correctly ripped (a near-'perfect' replica) with proper settings (like enabling subchannel and DPM capture) with using capable hardware, and the software that mount the disc image correctly interprets the DPM and subchannel data (emulators, hypervisors, or virtual drive software with optical drive hardware emulation capability), games should be run without emulation of copy protection or NoCD/NoDVD executable patches. SecuROM may require precise DPM timing, which emulation settings help simulate. Also, SafeDisc may expect specific error codes or sector access patterns, which the virtual drive must emulate. However, success is not guaranteed even in these cases: as the game’s protection code may still expect drive-specific behaviors (or by a drive with specific characteristics or firmware) that virtual drive solutions (emulators, hypervisors, or virtual drive software with optical drive hardware emulation capability) does not provide, causing the protection check to fail. If that is the case; mount the image in virtual drive software like Alcohol 120% or Daemon Tools with emulation settings (e.g., SecuROM, SafeDisc, SCSI/IDE mode) to mimic the behaviour. For instance, VirtualBox’s parser is very strict, it does not recognize the multi-track disc image or FLAGS DCP, so it throws: VERR_NOT_SUPPORTED. VMware on the other hand only supports ISO images. Daemon Tools v2 / encrypted MDF/MDS images are not supported by 86Box.[9] Ymir (v0.2.0 and later) introduces low-level CD Block emulation, which requires a valid CD Block ROM and enhances accuracy for CD drive operations and game commands.[10]

Niche Cases
 - Multi-Session Discs: Some CDs (e.g., mixed-mode or enhanced CDs) use multiple sessions, requiring formats like MDF/MDS or .aaruf to capture session metadata accurately.
 - Hybrid Discs: Discs with both CDFS/ISO 9660 and UDF partitions need formats like MDF/MDS or .aaruf to preserve both file systems.
 - Firmware-Specific Protections: Protections like Tages may require drives with specific firmware to read unique identifiers, complicating ripping.
 - Obsolete Dependencies: Some discs rely on external software (e.g., old DRM drivers) that may conflict with modern systems, requiring emulation or virtualized environments.
Limitations

DPM variability prevents perfect 1:1 copies, and protections like SecuROM 7+ or StarForce 3+ may require online activation, which images cannot replicate. Modern Windows (NT 10) blocks SecuROM/SafeDisc drivers; Microsoft intentionally blocked the secdrv.sys driver used by SafeDisc and SecuROM due to perceived security vulnerabilities, making these older disc-based games unplayable on modern Windows versions without workarounds (like noCD/noDVD executable patches or specific shims (e.g., SafeDiscShim), or using older OS environments e.g., Windows XP in a VM). Even a “perfect” rip does not guarantee usability. The emulator or media player software must still support the relevant disc features. For example, VLC uses libdvdcss, libdvdread and libdvdnav for copy protected DVD Videos. There are workaround methods for BD Video discs as well. DuckStation requires an .SBI file for LibCrypt-protected PAL titles even when subchannel data is present.[11][12] Software developers often avoid fully reproducing low-level drive behavior due to legal risk or copyright concerns, and the significant reverse engineering effort involved. Instead, they usually rely on workarounds such as patches, plugins, libraries, decryption methods or sidecar files (e.g., .sub, .sbi, or .m3d) to bypass protections rather than emulate them precisely.

Hardware-based protection

Amigados long track / Short tracks, MFM long tracks, Weak bit / Flakey bit types measures which used in Amiga software to many arcade systems hardware protection measures such as dongles, custom board or chip. Emulator projects for home console variants of these systems often bypass these protections due to key encryption and copyright concerns (see Legal status of emulation). Additionally, the effort required to overcome these protections often outweighs the potential benefits. These should not be confused with accessories designed for home media playback capability, like the Xbox DVD Movie Playback Dongle, which are typically sold separately due to licensing fees.

Examples;

See also

Reverse-engineering work on various systems helps us understand copy and hardware-based protection methods.

References

  1. ↑ Tom Clancy's Rainbow Six: Vegas 2 Anti-piracy
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