The article seems to be saying that 40 million in-store customers had their payment information stolen and that the 70 million people come from a different data set. The second data set includes "mailing and email addresses, phone numbers and names", so I wonder who would be included there. As a shopper, I have never given them any of that information, but I did when I applied for a job. I think it would also include people who have the Target credit card and anyone who has bought stuff from their website. I am not sure if their website is limited to US/Canada only.
I am not sure what I can really do about it. My debit card is set to email me if I have any charges greater than a dollar and my credit card (that I have not used at Target in a couple of years) has a tiny limit so it would be pretty much useless to anyone. I got my credit reports a few weeks ago and everything looked fine.
What type of account are you referring to?