rmogull writes "Brian Krebs over at the Washington Post just published a story that Heartland Payment Systems disclosed what may be the largest data breach in history. Today. During the inauguration. Heartland processes over 100 million transactions a month, mostly from small to medium-sized businesses, and doesn't know how many cards were compromised. The breach was discovered after tracing fraud in the system back to Heartland, and involved malicious software snooping their internal network. I've written some additional analysis on this and similar breaches. It's interesting that the biggest breaches now involve attacks installing malicious software to sniff data — including TJX, Hannaford, Cardsystems, and now Heartland Payment Systems." One bit of good news out of this massive breach is that, according to Heartland's CFO, "The nature of the [breach] is such that card-not-present transactions are actually quite difficult for the bad guys to do because one piece of information we know they did not get was an address." Heartland just put up a press release on the breach.