The U.S. Department of Homeland Security on 22 June issued a National Terrorism Advisory System bulletin warning of a “heightened threat environment” across the country after American forces bombed three Iranian nuclear facilities the previous evening. The notice, valid until 22 September, is the first nationwide advisory since Washington joined Israel’s campaign against Tehran’s nuclear program. While the bulletin cites no specific or credible threats, it says low-level cyber intrusions by pro-Iranian hacktivists are likely and that Iranian government–affiliated actors may attempt more serious network attacks. Violent extremists in the United States could also be inspired to act—particularly if Iran’s leadership issues a religious call for retaliation—raising the risk of shootings, bombings or antisemitic hate crimes. DHS notes that U.S. law-enforcement agencies have disrupted multiple potentially lethal Iranian-backed plots since 2020. Secretary of Homeland Security Kristi Noem said the department’s duty is “to keep the nation safe and informed, especially during times of conflict,” urging citizens to report suspicious activity and follow cybersecurity best practices. Police in New York City, Los Angeles, Washington and other major metropolitan areas have deployed additional patrols to religious, cultural and diplomatic sites as a precaution. Federal and local officials stress there is no immediate danger but advise heightened vigilance throughout the summer. The advisory follows President Donald Trump’s order on 21 June to strike Iranian nuclear sites, a move he said was intended to halt Tehran’s atomic ambitions. Human-rights groups estimate the Israel–Iran fighting has left more than 650 people dead in Iran and at least 24 in Israel, intensifying concerns that the conflict could spill over onto U.S. soil.