Sometime in the late 20th Century, Yoshi Iwatsu and Doctor Ito release a virus into the Internet that they created to destroy all nano–technology. 50 years later, around 2045 and 2055 AD, the virus gains independent freewill and returns to the present as a nanite robot called Proteus to kill Bloodshot and take the nanites from his veins.
After Bloodshot discovered Proteus's susceptibility to electro-magnetic fields, he lured him to the arctic circle and trapped it in tons of ice, although the trap did not destroy him.
Once Proteus recovered enough, he summoned Jillian Alcott to the arctic circle and she helped break free. Having failed to stop Bloodshot, Proteus changed his goal from destroying nano–technology to populating the Earth with nanite-enhanced beings, an objective that began with changing Bloodshot and Jillian’s twins into nanite beings like himself.
In a last ditch attempt to stop Proteus with an anti-virus developed specifically for him, Bloodshot detonated a massive bomb that seemingly killed them both.