The credit reporting agency, Equifax, announced on Sept. 7 that a hack has impacted the credit histories of up to 143 million Americans. Here's what you should do if you believe you are affected. (Jhaan Elker/The Washington Post)

Consumers affected by the Equifax data breach are scrambling for ways to protect their financial lives. Some are considering Equifax's own credit-monitoring service. Others suggest freezing your credit as a better option to such services. But what does freezing your credit entail, and how easy is it to do (and undo)?

In basic terms, freezing your credit means placing restrictions on who can view your credit report. Why is this important? Well, applying for housing, checking accounts or new credit cards can all involve a credit pull by potential landlords, mortgage lenders or banks. If you prevent them from pulling your credit, it'll frustrate the fraudsters who need these organizations' approval to open fake accounts using your stolen identity.

Freezing your credit comes with a $5 to $10 charge for each credit bureau. The amount of the charge depends on where you live; here's a PDF from Equifax that shows how much it might cost you. Often, victims of identity theft can freeze their credit at no charge. To get the ball rolling, visit the relevant websites of Experian, Equifax and TransUnion. You can also call Equifax (1-800-349-9960), Experian (1‑888‑397‑3742) or TransUnion (1-888-909-8872).

The credit agencies will ask for your personal information, including your name, address, date of birth and Social Security number. Once you've supplied those and frozen your credit report, nobody except your existing lenders, or their debt collectors, will be able to see it, according to federal regulators. The only other entities that are allowed to see your credit report at this point are government agencies carrying out a search warrant or subpoena, and yourself, if you're trying to access the free credit report that is entitled to you once per year per credit bureau. (You can thank a 2003 law known as FACTA for this right. Annualcreditreport.com is the only website you'll ever see government officials recommend for this purpose.)

But what do you do once your report is frozen and you need, say, a credit card company to look at it?

In that case, you can contact the credit bureaus again and ask them to lift or “thaw” the freeze. To do so, you'll need a PIN that your credit bureau gave you when you enabled the freeze. The reporting agencies are required to put the thaw into effect no later than three business days after you submit the request. You can also choose to lift the freeze only for a specific amount of time, to limit your exposure. Lifting the freeze can also come with a small fee.

If you lose your PIN, you can reset it, but that will typically require you to provide proof of your identity. This poses a different type of security risk; if a criminal manages to get a copy of the required identifying documents — say, through a corporate data breach or by persuading you to give up the information voluntarily through an email phishing attack — then there isn't much standing between a determined thief and an unfrozen credit report.

Still, many Americans become identity theft victims every year simply because they represent the easiest targets. Making it even a little bit harder for criminals to put your stolen identity to use could save you an enormous headache.

Read more:

People have been signing up for Equifax’s help service. Here’s what they were told.

How Equifax hackers might use your Social Security number to pretend they’re you

Why it can take so long for companies to reveal their data breaches