Insider attacks continued to haunt government agencies and companies alike in 2012. From rogue PIN pads at Barnes & Noble to disgruntled employees walking out with a nation's secrets, organizations suffered a wide variety of attacks.

While studies have found that insiders typically account for a minority of incidents, they tend to cause more damage, especially when privileged users, who have access to a company's crown jewels, go rogue. In addition, negligent insiders cause nearly 40% of all data breaches, and malicious attacks account for a third of incidents, according to a March study.

"The difference with insiders is they can inflict measurable financial, measurable IP, measurable brand and reputation damage -- more so than an outsider can," said Jim Butterworth, chief security officer for HBGary, a subsidiary of ManTech International. "Make sure that your employees, especially those with access to the crown jewels, are held accountable."