The numbers were mistakenly printed near the space designated for the recipients' name on quarterly newsletters sent out by Union Bank & Trust, which manages the state's Bright Directions tuition program, the Chicago Tribune reported Wednesday.
The bank says it has sent letters to Bright Directions participants offering free identity theft prevention services as well as credit monitoring.
Bridget Byron, director of college savings for the treasurer's office, said the data breach was relatively low-risk because the envelopes were sorted by machine and only handled by mail carriers delivering the letters to individual residences. She told the Tribune the treasurer's office and Illinois attorney general will follow up with Union Bank to plan stricter controls for using Social Security numbers.
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