The 20-something couple with a history of small-time scams had inadvertently hacked the world’s most powerful nation for a five-figure ransom at a time of high anxiety over national security on Inauguration Day. The Romanians had launched hundreds of thousands of emails embedded with ransomware in an attachment disguised as an invoice, authorities said. The list of email addresses they bought included, by chance, the Washington, D.C., police department. A recipient there apparently took the bait, opening the attachment that locked up the street-camera system. Only a payment could produce the key. Ms. Cismaru sent a message to the Journal...