Arcade operators and manufacturers have employed various methods throughout the decades to protect their lucrative games from piracy and unauthorized copying. A primary line of defense was hardware-based security. Many arcade PCBs (Printed Circuit Boards) used custom-made chips, such as CPUs with undumped microcode or special protection circuits. These chips were difficult to reverse-engineer and were essential for the game to run. If a bootleg copy was inserted, the game would often fail to boot or display graphical glitches and crashes due to the missing or mismatched hardware.

Another common technique was checksum verification. The game's code would perform a checksum or CRC calculation on the ROM chips during startup. The authentic ROMs would produce a specific expected value. Bootleg ROMs, which were often poorly copied or altered, would fail this checksum test. This failure could trigger various responses, from a simple warning message on screen to the game deliberately malfunctioning, making it unplayable. Famous examples include the "BAD ROM" error in some games or even secret, built-in countermeasures. In the game "R-Type II," a pirate copy would cause the player's ship to explode immediately after the first level began.

Piracy was also deterred through legal and business means. Manufacturers maintained close relationships with arcade distributors, making it difficult for operators to source obvious bootleg hardware without repercussions. The threat of legal action served as a significant deterrent against large-scale operations.

In the modern era, with the rise of digital distribution and online-connected cabinets, encryption and online verification have become the standard. Games are now often tied to a specific hardware dongle or require an online authentication check with a central server to verify the legitimacy of the software before it will operate. This continuous handshake between the game and the manufacturer's server makes modern arcade piracy extremely difficult. While determined pirates have historically found ways around many protections, the combination of hardware security, code obfuscation, and legal pressure has been largely effective in protecting the arcade industry's intellectual property.