Equifax, one of the “big-three” U.S. credit bureaus, said today that a data breach at the company may have affected 143 million Americans, jeopardizing consumer Social Security numbers, birth dates, addresses and some driver’s license numbers.

In a press release today, Equifax [NYSE:EFX] said it discovered the “unauthorized access” on July 29, after which it hired an outside forensics firm to investigate. Equifax said the investigation is still ongoing, but that the breach also jeopardized credit card numbers for roughly 209,000 U.S. consumers and “certain dispute documents with personal identifying information for approximately 182,000 U.S. consumers.”

In addition, the company said it identified unauthorized access to “limited personal information for certain UK and Canadian residents,” and that it would work with regulators in those countries to determine next steps.

“This is clearly a disappointing event for our company, and one that strikes at the heart of who we are and what we do. I apologize to consumers and our business customers for the concern and frustration this causes,” said Chairman and Chief Executive Officer Richard F. Smith in a statement released to the media, along with a video message. “We pride ourselves on being a leader in managing and protecting data, and we are conducting a thorough review of our overall security operations.”

Equifax said the attackers were able to break into the company’s systems by exploiting an application vulnerability to gain access to certain files. It did not say which application or which vulnerability was the source of the breach.

Equifax has set up a Web site — https://www.equifaxsecurity2017.com — that anyone concerned can visit to see if they may be impacted by the breach. The site also lets consumers enroll in TrustedID Premier, a 3-bureau credit monitoring service (Equifax, Experian and Trans Union) that is also operated by Equifax.

According to Equifax, when you begin, you will be asked to provide your last name and the last six digits of your Social Security number. Based on that information, you will receive a message indicating whether your personal information may have been impacted by this incident. Regardless of whether your information may have been impacted, the company says it will provide everyone the option to enroll in TrustedID Premier. The offer ends Nov. 21, 2017.

ANALYSIS

A time of publication, the Trustedid.com site Experian was promoting for free credit monitoring services was only intermittently available, likely because of the high volume of traffic following today’s announcement.

Several readers who have taken my advice and placed security freezes (also called a credit freeze) on their file with Equifax have written in asking whether this intrusion means cybercriminals could also be in possession of the unique PIN code needed to lift the freeze.

So far, the answer seems to be “no.” Equifax was clear that its investigation is ongoing. However, in a FAQ about the breach, Equifax said it has found no evidence to date of any unauthorized activity on the company’s core consumer or commercial credit reporting databases.

I have long urged consumers to assume that all of the personal information jeopardized in this breach is already compromised and for sale many times over in the cybercrime underground (because it demonstrably is for a significant portion of Americans). One step in acting on that assumption is placing a credit freeze on one’s file with the three major credit bureaus and with Innovis — a fourth bureau that is often used by businesses but overlooked by consumers.

For more information on the difference between credit monitoring and a security freeze (and why consumers should take full advantage of both) can be found in this story.

I have made no secret of my disdain for the practice of companies offering credit monitoring in the wake of a data breach — especially in cases where the breach only involves credit card accounts, since credit monitoring services typically only look for new account fraud and do little or nothing to prevent fraud on existing consumer credit accounts.

The fact that the breached entity (Equifax) is offering to sign consumers up for its own identity protection services strikes me as pretty rich. Typically, the way these arrangements work is the credit monitoring is free for a period of time, and then consumers are pitched on purchasing additional protection when their free coverage expires. In the case of this offering, consumers are eligible for the free service for one year.

However, the company appears to be metering how many consumers can sign up for the service at one time, offering the service to many of those affected at a future “designated enrollment date.”

That the intruders were able to access such a large amount of sensitive consumer data via a vulnerability in the company’s Web site suggests that Equifax may have fallen behind in applying security updates to its Internet-facing Web applications. Although the attackers could have exploited an unknown flaw in those applications, I would fully expect Equifax to highlight this fact if it were true — if for no other reason than doing so might make them less culpable and appear as though this was a crime which could have been perpetrated against any company running said Web applications.

This is hardly the first time Equifax or another major credit bureau has experienced a breach that impacted a significant number of Americans. In May, KrebsOnSecurity reported that fraudsters exploited lax security at Equifax’s TALX payroll division, which provides online payroll, HR and tax services.

In 2015, a breach at Experian jeopardized the personal data on at least 15 million consumers. Experian also for several months granted access to its databases to a Vietnamese man posing as a private investigator in the U.S. In reality, the guy was running an identity theft service that let cyber thieves look up personal and financial data on more than 200 million Americans.

My take on this: The credit bureaus — which make piles of money by compiling incredibly detailed dossiers on consumers and selling that information to marketers — have for the most part shown themselves to be terrible stewards of very sensitive data, and are long overdue for more oversight from regulators and lawmakers.

It’s unclear why Web applications tied to so much sensitive consumer data were left unpatched, but a lack of security leadership at Equifax may have been a contributing factor. Until very recently, the company was searching for someone to fill the role of vice president of cybersecurity, which according to Equifax is akin to the role of a chief information security officer (CISO).

The company appears to have announced the breach after the close of the stock market on Thursday. Shares of Equifax closed trading on the NSYE at $142.72, up almost one percent over Wednesday’s price.

This is a developing story. Updates will be added as needed.

Further reading:

Are Credit Monitoring Services Really Worth It?

Report: Everyone Should Get a Security Freeze

How I Learned to Stop Worrying and Embrace the Security Freeze