"Facebook is discriminating against people based upon who they are and where they live," HUD Secretary Ben Carson said. "Using a computer to limit a person's housing choices can be just as discriminatory as slamming a door in someone's face."

The HUD accuses Facebook of allowing advertisers to exclude certain categories of people from seeing ads, including parents, people born outside the US, non-Christians, those interested in Hispanic culture or accessibility matters and a number of others who fall within the Fair Housing Act's protected class parameters. It also says Facebook let advertisers show ads only to men or women, and exclude people in certain zip codes from seeing ads.

The department hopes to "address unresolved fair housing issues regarding Facebook's advertising practices and to obtain appropriate relief for the harm Facebook caused and continues to cause." Facebook settled a lawsuit related to discriminatory ads this month -- it said it would further limit targeting options for credit, employment and housing ads. It removed around 5,000 other targeting options in August.