One malicious email sent to South Carolina government employees let a hacker gain access to 3.8 million tax returns — and 1.9 million Social Security numbers and information on 3.3 million bank account information along with them. That cyber-attack on the state's Department of Revenue is the largest ever against a state government, according to a state-commissioned report by a computer security company. That study was released Tuesday, just as South Carolina Gov. Nikki Haley accepted the resignation of her Department of Revenue director and admitted that state officials "could have done more" to protect taxpayers' personal information. Her comments came amid a firestorm of criticism in her state over her handling of the massive data security breach and a heated dialogue over how states should best defend their data. South Carolina had never encrypted Social Security numbers, although it had encrypted credit card numbers, and on Tuesday Gov. Haley blamed the federal government for not requiring the state to do so.