Starting today, most United States visa applicants will have to provide information regarding their social media, The Hill reported.

A U.S. Department of State official told Hill.TV that the change will apply to both temporary and permanent applicants. A drop-down menu will require people to name their accounts or say that they don’t use social media. The information provided will be incorporated into a background check.

“This is a critical step forward in establishing enhanced vetting of foreign nationals seeking entry into the United States,” the official said in a statement to Hill.TV. “As we’ve seen around the world in recent years, social media can be a major forum for terrorist sentiment and activity. This will be a vital tool to screen out terrorists, public safety threats, and other dangerous individuals from gaining immigration benefits and setting foot on U.S. soil.”

Right now, the drop-down menu only includes “major” social media sites. There’s no clarification on which sites count as major. The administration does have plans to expand options, so applicants can eventually list all the sites they use.

The new policy isn’t coming out of the blue, but from an executive order President Donald Trump signed last year. Trump’s proposal was previously criticized by groups like the American Civil Liberties Union (ACLU).

Hina Shamsi, director of the ACLU’s National Security Project, said:

“This attempt to collect a massive amount of information on the social media activity of millions of visa applicants is yet another ineffective and deeply problematic Trump administration plan. It will infringe on the rights of immigrants and U.S. citizens by chilling freedom of speech and association, particularly because people will now have to wonder if what they say online will be misconstrued or misunderstood by a government official. We’re also concerned about how the Trump administration defines the vague and overbroad term ‘terrorist activities’ because it is inherently political and can be used to discriminate against immigrants who have done nothing wrong. There is a real risk that social media vetting will unfairly target immigrants and travelers from Muslim-majority countries for discriminatory visa denials, without doing anything to protect national security.”

Millions of people will be impacted by the new policy. It will take a while to fully know its impact.