Cybersecurity investigators noticed an unusual software crash late last year that only affected a small number of smartphones belonging to people who worked in government, politics, tech and journalism. Because the crashes have carried into 2025, they indicate a cyberattack that may have allowed hackers to infiltrate a phone without the user doing anything. Foreign hackers have increasingly identified smartphone and other mobile devices as a weak link in U.S. cyberdefenses, causing increased attacks on those devices.