My debit card was one of the potentially 4.2 million exposed in the recent Hannaford data breach. Here’s part of the letter from my bank, the Savings Bank of Walpole.

I’ve thanked them privately, and want to thank them publicly as well, for being proactive and doing the right thing here. They’re dealing with fallout from a problem they didn’t create.

Details are still emerging but we don’t yet have the full story. As the InfoWorld story notes, Hannaford’s servers might have been compromised by a remote exploit through the network, or a local exploit made possible by unauthorized physical access.

In the aftermath, most of the usual defense-in-depth strategies are being rehashed, and that’s good. But one-time account numbers still aren’t on the radar screen, and I keep on wondering: Why not?