A forthcoming study assesses all known information relating to the 419 breaches that were publicly disclosed in the U.S. in 2011. The majority of data breaches stem from hack attacks, followed by data that’s lost while physically in transit. Of all known breaches, 62% involved the exposure of social security numbers and 27% involved credit or debit card data. The government and armed services saw the greatest volume of records exposed (comprising 44% of all exposed records), followed by non-financial businesses.”]
Source: https://www.darkreading.com/attacks-breaches/hack-attacks-now-leading-cause-of-data-breaches