Nation states have clearly taken aim at Google - the company sends out 4,000 warnings about state-sponsored cyberattacks each month, Google Senior Vice President and Alphabet board member Diane Greene said at a Fortune magazine tech conference in Aspen, Colo., according to Reuters report.

The tech giant had previously said it was issuing tens of thousands of warnings every few months, which often prompted customers to upgrade their security in response, the report said.

When the notifications were introduced, they first appeared as thin red bars along the top of users' inboxes. But Google redesigned the notifications a few short months ago to take up the entire screen..

The move comes as the U.S. Justice Department aggressively pursued charges against several groups of state-sponsored hackers this year, including three alleged members of the Syrian Electronic Army (SEA).