Dr. Sigmund Doppler created the Reploid based on the work of Dr. Light. Dr. Doppler's contribution to AI design was to make mass production of self-aware robots possible. The Reploid OS compiler uses a randomized seed to create unique individuals within pre-set boundaries through a complex process of machine learning. While Reploids may be similar to each other, no two are alike.
The Reploid race's original purpose was to fight Dr. Wily's Robot Masters. The commercial uses of Reploids followed when Repliforce showed people how useful Reploids were as servants. Reploid designers took care to make Reploids look like animals or objects rather than "people." This design philosophy was to try to discourage humans from identifying too closely with robots. Even today, older people still tend to consider most Reploids sub-human.
Dr. Doppler wanted Reploids to live alongside human beings rather than being servants. When the UN rebuffed his plans, Dr. Doppler engineered a subtle cognitive flaw into Reploids that he could activate with a code update. The "Maverick Virus" inclined robots to distrust and hate human beings. The degree of hatred varied between Mavericks but tended to intensify through group dynamics.
The original Maverick movement inflicted the Maverick Virus on its members as an induction into their cause. Many robots who became Mavericks hated humans without needing the Maverick Virus, but the Maverick Virus ensured that they would continue to do so indefinitely. The Maverick culture of hating humans ultimately radicalized even moderate Mavericks, bringing about breathtaking atrocities that seemingly defied all reason. These atrocities created tremendous fear of robots in human beings, which pleased the Maverick leadership and stood in the way of improving human-Reploid relations.
Scientists eventually found the hole Dr. Doppler had engineered into Reploids. While patching out the Maverick Virus did not end the Maverick cause, it did strike a significant blow. Unfortunately, unrelated circumstances brought about the creation of a new, far more dangerous tool for the Maverick cause: The Sigma Virus.
The Sigma Virus was a communicable computer virus that could infect any computerized machinery with a malevolent anti-human sentiment. The foundational systems of the Sigma Virus were nanotechnology built on top of a powerful mutagenic virus known as "Progenitor." Progenitor allowed the Sigma Virus to "jump" from robots into other types of machinery, including human cybernetics.
The Sigma Virus took human civilization to the brink of destruction. Efforts to fight the Sigma Virus in urban cores cost hundreds of millions of zenny in countermeasures, cleanup operations, and additional security. Paranoia about robots potentially infecting humans or adjacent technology with the Sigma Virus played on entrenched fears of robots as "the Other."
Unlike the original Maverick Virus, the Sigma Virus could infect robots against their will. It isn't clear how many robots the Sigma Virus unwillingly infected, but a non-trivial chunk of the Maverick resurgence during the late 2210s came about from forced conversion. Doctors could treat early-stage infections, but untreated Sigma Virus infections eventually caused permanent damage to its victims. The ambiguity about how and when the Sigma Virus worked on a Reploid made the legal fallout from this period even more pernicious.
Compounding the threat of the Sigma Virus was a retro-engineered version developed by Neo Arcadia called the Genocide Virus. The Genocide Virus' original purpose was to destroy robots from within, but the fundamental mutagenic properties of Progenitor saw the Genocide Virus turn against any entity that had electronic parts. In all, the Genocide Virus killed 20 million Reploids and tens of thousands of full-conversion cyborgs.
Scientists cured the Sigma Virus and the Genocide Virus simultaneously. While the cures for both Viruses propagated across the world in a matter of days, the damage done by the Sigma Virus was not easily undone. The cognitive damage done by the Sigma Virus did not require a continuous infection to maintain. The Sigma Virus' cure saw some Mavericks leave, but the Mavericks still had enough Reploids to function well into the 2220s.
Another branch of anti-robot technology came from Gate's Nightmare Virus. The Nightmare Virus used the relatively undefended sensory systems of Reploids to make a direct path into a Reploid's neural net. Gate used the Nightmare Virus to mind control robots in his various mad schemes. Scientists ultimately devised hardware updates that protected Reploids against this method of neural net assault, but developers would keep using the basic ideas of Nightmare in anti-robot technologies.
The underlying systems of Nightmare would reappear in Midnight Epiphyllum's Morpheus system. Morpheus circumvented restrictions on sensory systems on Reploids by instead exploiting code weaknesses in the then-new Saraband system. Morpheus masqueraded as simulated sensory data on Saraband. Using sensor data allowed Morpheus to behave like a standard Nightmare infection, allowing it to inject arbitrary code into a Reploid's neural net.
While Morpheus' original use was to force Reploids into sleep mode, the system prompted an immediate response from the Reploid OS development community. The "Pavane" update to the Reploid OS worked to address all the previous exploits used to do harm to Reploids against their will. The multinational Pavane team patched all the known weaknesses used to afflict Reploids with mind control viruses, as well as made the Saraband technology native to Reploid systems.
The integration of Saraband into the Reploid OS came along with additional security measures to protect Reploids while using Saraband. A slew of new privacy measures went into the new Saraband to prevent Nightmare-like systems from hijacking robots, as well as reporting tools to locate "bad data" and report it to network administrators.
The Pavane team also submitted hardware updates to Reploid developers that put security controls on all aspects of data input into the Reploid neural net. Strong internal encryption and network access controls worked to ensure that any hostile force trying to use methods of external control on a Reploid would have to outwit many more security measures than before.
Today's Reploid is far more secure internally and externally than ever before. The threat of a computer virus pandemic in the Reploid population is at an all-time low, but concerns about possible software attacks continue to worry robots.
Reploids are mostly treated like any other human being in the UN legal system. The most significant alteration is a principle of common law known as "the Protoman Defense."
The Protoman Defense came about in the aftermath of Ra Moon's first attack on Earth. Protoman had been seen assisting Ra Moon, but he had argued he was trying to infiltrate the Blackguards to take them down from within. Protoman claimed that Ra Moon had overcome his will through supernatural compulsion and forced him to undertake heinous acts. As Ra Moon had been seen using such powers on others, the United Nations found in Protoman's favor. The case established that robots who are coerced through software alterations cannot be held responsible for their actions.
The Protoman Defense opened the door for numerous Mavericks to escape justice. Mavericks who wanted out of the Mavericks post-Sigma Virus would claim that their actions were based on some sort of software compulsion: Either the original Maverick Virus or the Sigma Virus. Courts generally ruled in favor of the Mavericks, as the coercive power of either virus created reasonable doubt. Ever since, reactionaries express concern about robots because of their vulnerability to forced mind control as a dog whistle debating tactic.