hacking

This 2010 image, provided by IntelCenter, shows Humam Khalil Abu-Mulal al-Balawi in a posthumous video message posted on extremist websites. The al-Qaida double agent killed seven CIA operatives, a Jordanian spy and himself when he set off a bomb strapped to his body at a base in Afghanistan in December 2009. AP/IntelCenter hide caption

In January, the hacker group Anonymous staged a demonstration at a BART station in San Francisco after officials turned off cell phone service in its stations. Justin Sullivan/Getty Images hide caption

When it comes to Internet security these days, even seemingly secure passwords aren't usually enough to stop hackers. ragsac/iStockphoto hide caption

Citigroup said it discovered the breach in early May through routine monitoring. Mark Lennihan/AP hide caption