Excellus discovered the breach on Aug. 5 and began notifying affected individuals earlier this week. Attackers may have gained access to personal information for as many as 10 million individuals, including name, date of birth, Social Security number, mailing address, telephone number, member identification number, financial account information, and claims information. The number of affected individuals include members of other Blue Cross Blue Shield plans who sought treatment at a facility located in the Excellus service area.