Until the process is complete, it has forbidden staff from removing Nasa-issued laptops containing sensitive information from its facilities. The order follows the loss of a device containing "sensitive personally identifiable information". There have been several similar incidents over recent years.
Nasa said the latest incident had occurred on 31 October, when a laptop and documents were stolen from a locked vehicle of one of its employees at Nasa headquarters in Washington DC. The machine was password protected, but the agency acknowledged that the information might still be accessible to hackers since it was not encrypted.
Encryption would have scrambled the data, requiring a complicated code to make it understandable again. As a result, Nasa has warned its workers to watch out for bogus messages.
"All employees should be aware of any phone calls, emails, and other communications from individuals claiming to be from Nasa or other official sources that ask for personal information or verification of it," an agency-wide email published by news site Spaceref stated.
"Because of the amount of information that must be reviewed and validated electronically and manually, it may take up to 60 days for all individuals impacted by this breach to be identified and contacted."