A cyberattack on the library system of Pierce County, Washington exposed the information of more than 340,000 people.

The Pierce County Library System published breach notifications this week on its website and with regulators in several states. The letters concern a cybersecurity incident that was first discovered on April 21 and required the library system to shut down all of its systems. 

By May 12, the organization confirmed that hackers breached their systems and stole information on employees and customers of the library – which has 19 locations and serves a county population of nearly 1 million people outside of Seattle. 

The letter says an investigation revealed the hackers had access to organization systems between April 15 and April 21. The information stolen varied between patrons of the library system and current or former employees. For those who use the library’s services, their names and dates of birth were leaked. 

For current or former employees, the data stolen includes Social Security numbers, financial account information, driver’s license numbers, credit card information, passport numbers, health insurance information and medical data. 

The attack was claimed by the INC ransomware gang in May. The group has launched several damaging attacks on government systems in 2025, including attacks on the Pennsylvania Office of the Attorney General and an emergency warning service used by municipalities across the U.S.

Pierce County previously dealt with a ransomware attack in 2023 on its public bus service that disrupted a system used by 18,000 people per day. 

Public library systems have repeatedly faced attack in recent years by ransomware gangs that believe demand for access to online library services will force governments to pay ransoms. 

In addition to high-profile attacks on massive systems like the British Library, multiple libraries across Canada and the U.S. have dealt with outages caused by ransomware attacks.  

The attacks on libraries across the globe has even prompted U.S. officials to propose the creation of a program specifically designed to collect data about the cybersecurity and advanced firewall services that would best help libraries defend themselves from hackers.