The hackers who stole the data of hundreds of millions of Yahoo users two years ago were two cybercriminal gangs, InfoArmor reported Wednesday. That finding contradicts the notion that state-sponsored actors were behind the attack, which Yahoo suggested earlier this month when it disclosed the breach. Further, the number of users' records stolen is closer to 1 billion than to the 500 million Yahoo acknowledged, according to InfoArmor. However, much of the data is useless, the firm said.