With device searches at American border crossings reaching an all-time high, the US Customs and Border Patrol (CBP) this week tightened its rules for when agents can pull data from phones and computers.

The updated directive [PDF] amends the 2009 CBP border search guidelines to require that agents at least have "reasonable suspicion" shown before they can use external equipment to connect and copy the contents of devices they encounter at border crossings.

"Basic" searches, where agents simply peer into the contents of a device, including photos, texts, and contacts, can still be conducted at random without a warrant nor reasonable suspicion.

"CBP is committed to preserving the civil rights and civil liberties of those we encounter, including the small number of travelers whose devices are searched, which is why the updated Directive includes provisions above and beyond prevailing constitutional and legal requirements," said John Wagner, CBP Deputy Executive Assistant Commissioner, in announcing the new policy.

"CBP’s authority for the border search of electronic devices is and will continue to be exercised judiciously, responsibly, and consistent with the public trust."

The new rules come as the CBP says it is rifling through more devices than ever. In 2017, searches rose by more than 50 per cent over 2016, with border cops reporting they searched 30,200 phones, tablets, and PCs at crossings. By comparison, 2016 saw a total of 19,051 searches.

Privacy advocate and influential US Senator Ron Wyden (D-OR) said that while "far too many" searches are being carried out by CBP, the new rules were better than nothing.

"I've said it before and I'll say it again: Americans' Constitutional rights shouldn’t disappear at the border. By requiring ‘reasonable suspicion’ before conducting forensic searches of Americans’ devices at the border, Customs and Border Protection is beginning to recognize what the Supreme Court has already clearly stated that ‘digital is different," Wyden offered.

"It is my view that Americans will be safer when time and resources are spent on searching people with an actual cause." ®