In early September, the world learned that the personal data of 143 million Americans, or about half the US population, was compromised by an free-roaming, multi-month penetration of Equifax. As one of three major US consumer credit reporting agencies, the historic breach and suspicious trading of shares by Equifax executives shortly after the breach was discovered moved the US Senate banking committee to convene a panel to question the former Equifax Chair and CEO Richard Smith.

With the Equifax breach, the sensitivity and comprehensiveness of compromised data escalated dramatically from password-email combinations that characterized attacks back in 2004 to complete personal identification records today. The quality of the information compromised by Equifax's failure is perhaps unparalleled except by the breach of the US Office of Personnel Management in June 2015, which affected 22.1 million* people who had undergone federal background checks and/or requested access to federal buildings.

The largest breach known to date occurred earlier this year when the email accounts, full names, IP addresses, and often physical address of more than 1 billion people were exposed by an attack on the email marketing organization River City Media.

A data breach often affects not only a company's reputation and customer loyalty but also the company's stock value, altering its revenue and cash flows for years to come.

Reduced EBITDA and revenue were the real cost of eBay 's data breach of May 2014. Market analysts continue to examine to what degree the breach was responsible for the 37 percent decrease in EBITDA and a nearly 50 percent drop in revenue a year later.

One year after JP Morgan Chase , one of the largest banking institutions and financial services holding companies in the US, was breached, the company’s sales had dropped by 7 percent, market value by 2 percent. The bank has reportedly also invested an additional $250 million in information security to better protect customer data.

In the case of the Home Depot —an American retailer of tools, construction products, and related services—the company’s financial performance was only marginally affected, however, its data breach cost the company over $130 million in compensation to Visa, MasterCard, and various banks.

* The original 21.5 million affected was revised upward to include the 4.2 million former and current federal employees whose personnel records were also breached.