Wow! Another retail/credit card breach, potentially 100 million credit cards at risk, as reported here:
Heartland Payment Systems, a credit card processor, announced today, January 20th, that up to 100 Million credit cards may have been disclosed in what is likely the largest data breach in history

Until we know more, it probably isn't fair to discuss the PCI compliance angle. But what initially struck me about this is that the last few really big retail security breaches have all involved malware being planted in the retailer/processors network. This software, after capturing card data has to send it somewhere, through some communications channel. To me the really obvious key questions are:

1) How did this software end up on the network?
2) How do we stop this from happening in the future?

The less obvious question is why didn't they spot this sooner? Presumably these attackers have to send the valuable data they are stealing out of the processors network, else it is worthless.  Richard Bejtlich wrote a terrific book, Extrusion Detection, that is a pretty thorough analysis of how to use Snort and other tools to look at outgoing (to the internet) data flows, and spotting anomalous behavior that is usually indicative a security problem, whether involving people or technology.  Sure it would be better to figure out how to stop this stuff getting on one's network in the first place. But putting an extrusion detection capability in place as a tripwire would be of great benefit in limiting the scope and duration of attacks like this.

Jim