Here's what you need to know:

What happened? Epsilon Interactive last Friday announced that unknown intruders had broken into one of its email servers and accessed the names and email accounts of some of its 2,500 corporate customers. Epsilon has not disclosed how many accounts in total were exposed in the breach. Some say it is the involving this kind of data, meaning that tens of millions of email addresses were likely compromised.

I've never heard of Epsilon. Why do they have my name and email address? Epsilon provides email and customer loyalty services to more than 2,500 corporations, including seven out of the top 10 Fortune 100 companies. The company sends more than 40 billion emails annually on behalf of these clients. So even if you haven't heard of them before, chances are high that your bank, favorite retailer, or hotel chain is using Epsilon for email and other services. The company touts itself as the world's largest permission-based email marketing provider and is believed to store more than 250 million email addresses.

How did the breach happen? Epsilon has not divulged any details of the breach beyond saying that it was discovered on March 30.

If it's only names and email addresses that were exposed, why is everybody acting so concerned? The Epsilon breach, big as it is, could have been much worse. Right now, the biggest concern is that the stolen email addresses will be used by the intruders to .