The audit found that the board needlessly retained the full nine-digit Social Security numbers of about 592,000 active and inactive voters in its data base — or almost 15 percent of the state's 4.1 million registered voters — when only the last four digits were needed. The report said the board then shared voters' personal information — including driver's license numbers and the last four digits of Social Security numbers — with a third-party organization without ensuring that the data was safeguarded.