It used to be that we didn’t care too much if someone stole a pile of email addresses. At worst we’d end up on yet another spam list, and these days most folks have pretty decent spam filters. Sure, it’s annoying, but it was pretty low on the scale of security risks.

But I’m starting to think that email addresses – depending on context – are now worth far more to certain attackers than credit card numbers.

As annoying as credit card fraud is, it’s generally a manageable problem. For us as consumers it’s mostly a nuisance, because we are protected from financial loss. It’s a bigger problem for merchants and banks, but fraud detection systems and law enforcement together manage to keep losses to an acceptable level – otherwise we would see Chip and PIN or other technologies, as opposed to PCI, as the security focus.

In terms of economics, we have seen bad guys shift to lower-level persistent fraud rather than big breaches. They’re stealing a lot, but the big lesson from the Verizon Data Breach Investigations Report is that they are stealing smaller batches, and are much more likely to get caught than in the past.

Your email, on the other hand, may be far more valuable. Not necessarily to random online street criminals (although it’s still valuable to them, too), but to more sophisticated attackers. At least if they get your email address with ‘interesting’ context.

Let’s look at the main method of attacks these days. From APT to botnets, we see one consistent trend – reliance on phishing to get past user defenses and gain a beachhead on the target. Get the user to click a link or open a file, and you own their system. “Spear phishing” (highly targeted phishing) has been identified as the primary attack technique currently being used by the APT – they will shift once it stops working so well.

Now think about last week’s breach of Sega, or back to the Epsilon breach. In these cases emails, first names, and context were obtained. Not just an email, but an email with a real name and a site you registered to receive email from.

We like to hammer users on how stupid they are for clicking any link in a storm, but what are the odds of even the most seasoned security professionals defending themselves from every single one of these attacks with, in effect, detailed dossiers on the targets? When you get a correctly formatted email with your name from a site you registered with, there’s a reasonable chance you will click – and they can easily afford to send more fishing messages than real mail (spam has been up as high as 90% of email on the Internet, and these are much better at looking legitimate and getting past spam filters).

Don’t play coy and claim you’ll check the From: address every time – these all come from services you don’t know personally, and often from a third party domain as part of the service.

Considering everything an attacker can do with those resources, I suspect email addresses + context might be the new bad guy hotness. Hit every TiVo subscriber with a personally addressed phishing message, perhaps modeled from the last email blast TiVo actually sent out? Gold.