Unlike the Equifax breach and some of the others, Capital One has not established a web-site where you can determine whether or not your information was compromised but instead promises to contact those whose information was leaked.
Since it is safe to assume that your personal data is on the dark net for criminals to purchase and exploit it is important for you to take a defensive stance. Here are some tips to secure your good credit and protect your assets:
Sign up for a credit monitoring service. I signed up with my bank and although it costs me $12 per month, it has saved me hours of grief. I get an e-mail whenever someone makes a credit inquiry. I also get notice of any changes in my credit scores and I can review three of the credit bureaus reports at any time. Here is a review of some of the credit monitoring services available. https://www.creditsesame.com/credit-monitoring/best-credit-monitoring-services-reviews/
If you do not want to spend a monthly fee you can get one free report from each of the three major credit bureaus annually. https://www.annualcreditreport.com/index.action
You can place a fraud alert on your account with each of the credit bureaus. This does not affect your credit score but warns creditors to be certain that it is you before granting new credit.
You can “Freeze your credit”. Again, you have to contact each of the credit bureaus. If your credit is frozen no one can open a credit account without you removing the freeze.
The internal revenue has some good advice in their publication 5027, https://www.irs.gov/pub/irs-pdf/p5027.pdf regarding identity theft. This document also includes links and telephone numbers to the three major credit bureaus.
The Federal Trade Commission provides good advice here, https://www.consumer.ftc.gov/features/feature-0014-identity-theft, which includes how to report identity theft.
Below is a link for a prior article regarding identity theft.