Credit-reporting service Equifax revealed a massive cybersecurity breach on Thursday that could affect up to 44 percent of the U.S. population. Even if you have never heard of the company, your personal information could be at risk. Here's what to do to keep yourself safe.

1. Know what information could be vulnerable and take it seriously

To calculate your credit score, Equifax pulls your financial information from institutions like banks and credit card companies, often without you even knowing. Even if you have never interacted with the company before, your information could be at risk. The hackers stole social security numbers, birth dates, and addresses of an estimated 143 million people. An additional 209,000 people had credit card numbers stolen, and 182,000 people had "personal identifying information" compromised, CNN Money reports.

2. Review your accounts

Credit card reports look fishy? Has there been activity in your accounts that definitely wasn't you? Report it to your bank ASAP. If you think you're the victim of identity theft, tell the police. Learn more about what to do if you think your identity has been stolen here at The Week, and read tips about how to protect yourself in the future here.

3. Change your passwords

Just to be safe, change passwords on all your sensitive accounts. Set up two-step authentication if you can. Need help finding a strong password? Learn more here.

4. Set up fraud alerts on your credit reports

Credit expert John Ulzheimer, a former employee of Equifax, told CNN Money that setting up alerts "means that a lender must contact you to verify your identity before it issues credit in your name. You can place an alert on your report for free by contacting one of the credit agencies, which is required to notify the other two. It will last for 90 days and can be renewed." To be safe, The New York Times recommends setting up fraud alerts at all three credit reporting agencies.

5. Consider freezing your credit

Fees to freeze your account usually cost between $5 and $10, but it means no one will be able to take out a loan in your name because a lender can't pull your report. "This will lock down your credit files permanently, so that only companies that you currently do business with can see them," the Times writes. Ulzheimer added: "It's a pretty extreme measure, but when 143 million people have been exposed like this, I think you have to take it."

6. Consider signing up for credit file monitoring and identity theft protection

Starting on Monday, Equifax is offering a year of free service through TrustedID Premier, which you can enroll in here (click the "check potential impact" tab). "The catch is, if you want to learn if your information — including your social security number — was compromised, you have to enter the last six digits of your social security number," Fast Company writes. "So, customers of a service intended to protect personal information are now being asked to enter the very data that's supposedly protected to learn if it's not. Seems a bit circular, no?" And there's another catch with using TrustedID Premier: "[Y]ou must agree to submit any complaints against Equifax to arbitration," CNN Money reports. "You can't sue on your own behalf, and you can't join a class-action case or benefit from any class-action settlement that Equifax agrees to."

As TechCrunch writes, "Until questions are answered, I would avoid using the site." Paying for your own credit monitoring service can get expensive, though. "Some services charge as much as $50 monthly to keep tabs on your credit, which can total $600 annually," The Wall Street Journal warns. The other credit agencies, Experian and TransUnion, offer their own services, as do many banks: "Look around, you might be able to get a better offer through your financial institution," The Wall Street Journal suggests. Consumer Affairs also rates Identity Guard highly, and the more popular LifeLock received mixed reviews.

Read more about how to protect yourself from identity theft at The Week.