What companies should be doing to protect their computer systems—but aren’t

That may be difficult to imagine if you follow the headlines. In late 2013, America entered the age of the megabreach when Target Corp. lost 40 million credit-card numbers to Russian-speaking hackers. Since then there’s been Home Depot Inc., Adobe Systems Inc., J.P. Morgan Chase & Co., eBay Inc., Anthem Inc., to name just a few.