Iranian hackers breached water systems across at least a dozen U.S. states, disabling safety alerts that warn operators of contamination. The intrusions expose decades of ignored vulnerabilities and budget cuts to the very federal agencies tasked with defending critical infrastructure, raising urgent questions about America's exposure to a new form of warfare. Iranian-linked hackers infiltrated water treatment facilities by exploiting basic security flaws in internet-facing remote-access systems, then disabled internal safety mechanisms that alert operators to problems.