WikiLeaks on Sunday released two CIA documents that offered tips to help spies maintain their cover while using false documents as they crossed international borders.
The two documents, dating from 2011 and 2012, are marked classified and "NOFORN," which means they were not meant to be shared with allied intelligence agencies, WikiLeaks said.
The documents outline a number of strategies for agents to avoid secondary screening at airports and borders.
One of the CIA documents, called "Schengen Overview," reveals that the CIA is very concerned about EU nations introducing biometric security measures for people traveling on US passports and that new systems pose an increased "identity threat" -- in other words, making it harder for agents to travel on false documents.
WikiLeaks founder Julian Assange said the documents show the CIA is intent on carrying out spying in Europe.