While the classic image behind data breaches is a shadowy hacker, a real risk, accidental or otherwise, is much more visible—your own employees. The Price Waterhouse Coopers Global State of Information Security Survey 2015 found that, in 2014, 35 percent of data breaches were caused by current employees and 30 percent by former employees. In a poll of attendees at the Infosecurity Europe 2014 Conference, 37 percent of respondents indicated that an activist employee was the biggest threat to data security, while only 19 percent cited cyberattacks as the worst threat. Hackers might labor for years to access data that employees can access almost immediately—even though the vast majority of employees would likely never do anything to intentionally cause a data breach.

There are safeguards companies can put in place, including strong employee monitoring and training, comprehensive plans to deal with breaches and policies for work with third parties. But companies should realize that protection against breaches needs to start from within.