The National Counterintelligence and Security Center began sending out detailed advisories, in brochure and video forms, to companies around the country to show them how to guard against cyber-incursions.

The blitz follows hotel chain Marriott’s disclosure last week that hackers stole more than five million passport numbers of guests at its properties.

It was the latest in what the Trump administration says has been a surge of attacks on government and corporate computer systems, especially by Chinese intelligence, seeking to steal business secrets and databases.