“It appears that even if a friend or associate has not directly interacted with the applicant on social media, the agency will ferret out connections,” a group of 11 civil liberties groups said in a letter commenting on the CBP proposal.

The United Nations special rapporteur on the right to freedom of opinion and expression wrote last month that the scope of information being collected was “vague and open-ended,” and that he was “concerned” that with the change, “government officials might have largely unfettered authority to collect, analyze, share and retain personal and sensitive information about travelers and their online associations.”

Privacy groups in recent weeks have pushed back against the idea, saying it could chill online expression and gives DHS and CBP overbroad authority to determine what kind of online activity constitutes a “risk to the United States” or “nefarious activity.”

U.S. Customs and Border Protection wants to start collecting “information associated with your online presence” from travelers from countries eligible for a visa waiver , including much of Europe and a handful of other countries. Earlier this summer, the agency proposed including a field on certain customs forms for “provider/platform” and “social media identifier,” making headlines in the international press . If approved by the Office of Management and Budget, the change could take effect as soon as December.

Soon, foreign visitors to the United States will be expected to tell U.S. authorities about their social media accounts.

“If a ‘follower’ of an applicant raises a red flag for the agency, the applicant herself may be denied permission to travel to the United States.”

CBP and its parent agency, the Department of Homeland Security, said that the social media question will be optional, and that the agencies “would only have access to information publicly available on those platforms, consistent with the privacy settings of the platforms.”

A CBP spokesperson provided a statement saying that collecting social media information “may help detect potential threats because experience has shown that criminals and terrorists, whether intentionally or not, have provided previously unavailable information via social media that identified their true intentions.” The statement also said that “the collection of social media identifiers will not be used to prevent travel based on applicant’s political views, race, or religion.”

The CBP spokesperson did not say whether leaving social media information off an application would adversely impact someone’s visa waiver application, or flag them for extra screening, saying only that the application could still be submitted without it.

Earlier this month The Intercept detailed how CBP works closely with the FBI to screen passengers as potential informants, passing the bureau information gleaned from travel records and secondary screenings. The goal was “looking for ‘good guys,’ not ‘bad guys,’” in the words of one of the FBI documents.

The American Civil Liberties Union said that the documents appeared to show CBP conducting “unduly invasive” questioning, and “using the border as a dragnet for intelligence gathering on innocent people.” It is precisely that kind of program that privacy advocates are worried about when it comes to ordinary travelers turning over their online lives to border authorities.

“We know that they are going to use this for ‘contact chaining,’ or ‘two-hop’ analysis,” said Nathan White, of the internet freedom advocacy group Access Now, referring to the practice of looking not just at someone’s contacts but also their contacts’ contacts. “Apply that to social media and imagine they’re interested in a friend of a friend of the traveler to recruit as an informant. They could see all those connections.”

Access Now and other groups also noted that by looking at the social presence of foreigners, DHS will inevitably suck up, retain, and share with other agencies huge amounts of information on Americans who are connected to them, even in a tangential way.

In order to institute the change, the CBP had to open the proposal for public comments. That period ended earlier this month, and now the Office of Management and Budget has 60 days to ask the agency to amend the proposal or sign off on the change. The OMB doesn’t evaluate the change for privacy or civil liberties implications, but rather from a paperwork and cost standpoint.

“To the OMB, we’re making the argument that it’s expensive to collect this, and it’s useless — only innocent people are going to give you their real information,” said White.