About three months ago, Google started notifying some Gmail users that they might be the targets of state-sponsored attacks. As one of the most popular email services in the world, Gmail is an obvious target for any government trying to keep its citizens in check.
Google has been monitoring the attacks and trying to deflect them, but took a more active role in June when it believed it could determine with enough accuracy whether one account was targeted or not.
Since then though, Google has found that the problem is significantly bigger than it initially thought. In fact, Google will now start sending out these messages to tens of thousands more people, as its methods for detecting suspicious activity have improved.
While the tool may have been developed to target Chinese attacks, not that Google will ever say that, there are far more governments involved in this than you'd imagine. Google says that it's seeing an increase in attempts from Middle East countries.