They know where you live, how old you are, and if they get their way, border agents might even find out your Twitter handle.

The U.S. Department of Homeland Security has put in a proposal to collect social media details from some non-immigrant visitors coming into the country.

If approved, the offering of social media data would be voluntary and added as a question to the Electronic System for Travel Authorization (ESTA) — used to see if a traveller from a Visa Waiver Program country is able to travel to the U.S. without a visa — as well as on the I-94W. That's used at the land border in lieu of an ESTA for Visa Waiver Program travellers coming to the U.S.

Canadian citizens would be exempt as they do not need an ESTA or an I-94W to enter the U.S. However, it would apply to other types of residents, such as those hailing from countries that are part of the U.S.'s Visa Waiver Program but live in Canada. Those countries include France, Australia and Japan, among others.

The security department said the social media info would be used "for vetting purposes, as well as applicant contact information."

"Collecting social media data will enhance the existing investigative process and provide DHS greater clarity and visibility to possible nefarious activity and connections by providing an additional tool set which analysts and investigators may use to better analyze and investigate the case," their proposal reads.

U.S. Customs and Border Protection (CBP) — part of the DHS — told CBC News that visitors would be able to provide up to 10 social media names and handles, from their Facebook, Twitter and Instagram accounts, among others.

A CBP spokesperson said that DHS would only have access to information that's publicly available on these accounts — and that applicants wouldn't be punished if they chose not to provide this information.

They did not say how they would verify the accounts given.

More transparent?

Though the proposal said providing the social media info would be optional, some still have privacy concerns.

Christopher Parsons, a research associate at the University of Toronto's Citizen Lab, has issues with how the U.S. border authority could use the social media information.

"It can be very challenging in 140 characters to provide a full context of a joke or an association or something of that nature so it could lead to people being concerned," he told CBC News, pointing to past examples of joke tweets about security that went awry.

"Is what they said going to be used against them even though it was perfectly innocuous?"

But he said the fact that the DHS is asking for this information shouldn't come as a surprise because it's something border security is already tracking — he said this just makes it more transparent.

The U.S. has supposedly heightened its monitoring of social media amongst visa applicants in the wake of the San Bernardino shootings last December.

"This at least makes it much more evident I think to people who are coming in that this is an actual area of surveillance whereas previously perhaps people might have been a bit more surprised."

Parsons said the information could also be used for an alert system, to check in and make sure travellers are OK if an emergency or crisis happens while they are visiting.

Canada 'not considering'

The same measures the U.S. is proposing won't be coming to Canada anytime soon.

Lindsay Wemp, a spokeswoman for Immigration, Refugees and Citizenship Canada, said they are "not considering asking travellers to provide their social media account names when travelling temporarily to Canada."

The U.S. is soliciting public comment on its proposal until Aug. 22, after which it will be further considered.