The Pierce County Library System cyberattack has exposed the personal information of more than 340,000 individuals following a cybersecurity incident discovered in April 2025. The public library system, which operates 19 locations and serves nearly one million residents outside Seattle, confirmed that unauthorized access to its network resulted in sensitive data being copied and taken.
According to breach notification letters published this week on the Pierce County Library System (PCLS) website and filed with regulators in multiple states, the incident occurred between April 15 and April 21, 2025.
PCLS detected the breach on April 21 and immediately shut down its systems to contain the attack and begin an investigation.
Unauthorized Network Access and Data Exposure
The investigation revealed that attackers gained access to PCLS systems for nearly a week and exfiltrated files containing personal information. By May 12, the organization confirmed that hackers had stolen data belonging to both library patrons and current or former employees…