The FBI has uncovered evidence that foreign hackers penetrated two state election databases in recent weeks, prompting the bureau to warn election officials across the country to take new steps to enhance the security of their computer systems. The FBI warning [was] titled Targeting Activity Against State Board of Election Systems." The alert, labeled as restricted for "NEED TO KNOW recipients," disclosed that the bureau was investigating cyberintrusions against two state election websites this summer, including one that resulted in the "exfiltration," or theft, of voter registration data. The bulletin does not identify the states in question, but sources familiar with the document say it refers to the targeting by suspected foreign hackers of voter registration databases in Arizona and Illinois. In the Illinois case, officials were forced to shut down the state's voter registration system for 10 days in late July, after the hackers managed to download personal data on up to 200,000 state voters, Ken Menzel, the general counsel of the Illinois Board of Elections, said in an interview. FBI agents confirmed to [Menzel] that the perpetrators were believed to be foreign hackers, although they were not identified by country. Agents told him they had reached no conclusions, and other experts say the hackers could also have been common cybercriminals hoping to steal personal data on state voters for fraudulent purposes, such as obtaining bogus tax refunds.