The 2020 Census is at risk of being manipulated by bad actors online, a top official from the Government Accountability Office told the Senate Homeland Security and Governmental Affairs Committee on Tuesday.

Worries about a skewed population count come in a year in which the Commerce Department, the agency which oversees the Census Bureau, has already announced a need to increase the overall “end of project” cost of the 2020 census by more than $3.3 billion.