Major cybersecurity incident
Between May and July 2017, American credit bureau Equifax was breached. Private records of 147.9 million Americans along with 15.2 million British citizens and about 19,000 Canadian citizens were compromised in the breach, making it one of the largest cybercrimes related to identity theft. Equifax discovered the breach end of July, but did not disclose it to the public until September 2017. In a settlement with the United States Federal Trade Commission, Equifax offered affected users settlement funds and free credit monitoring.
In February 2020, the United States government indicted members of China's People's Liberation Army for hacking into Equifax and plundering sensitive data as part of a massive heist that also included stealing trade secrets, though the Chinese Communist Party denied these claims.
Data breach.
Information accessed in the breach included first and last names, Social Security numbers, birth dates, addresses and, in some instances, driver's license numbers for an estimated 143 million Americans, based on Equifax' analysis. 
Information on almost 14 million British residents was also compromised. as well as 8,000 Canadian residents. An additional 11,670 Canadians were affected as well, later revealed by Equifax. Credit card numbers for approximately 209,000 U.S. consumers, and certain dispute documents with personally identifiable information for approximately 182,000 U.S. consumers were also accessed.
Background.
An Equifax internal audit in 2015 showed that there was a large backlog of vulnerabilities to patch, that Equifax was not following its own timescales on patching them, that IT staff did not have a comprehensive asset inventory, that Equifax did not consider how critical an IT asset was when prioritising patches, and that the patching process worked on an 'Honour system'. The report set out actions to improve the process, but the time of the breach, two years later, many of them had not been completed. 
A key security patch for Apache Struts was released on March 7, 2017 after a security exploit was found and all users of the framework were urged to update immediately. Security experts found an unknown hacking group trying to find websites that had failed to update Struts as early as March 10, 2017.
Intrusion.
The breach at Equifax started on May 12, 2017 when Equifax had yet to update its credit dispute website with the new version of Struts. The hackers used the exploit to gain access to internal servers on Equifax' corporate network. The information first pulled by the hackers included internal credentials for Equifax employees, which then allowed the hackers to search the credit monitoring databases under the guise of an authorized user. Using encryption to further mask their searches, the hackers performed more than 9000 scans of the databases, extracted information into small temporary archives that were then transferred off the Equifax servers to avoid detection and removed the temporary archives once complete. The activities went on for 76 days until July 29, 2017 when Equifax discovered the breach 
Discovery.
On July 29, 2017, Equifax's internal IT team updated an SSL certificate for an application that monitored inbound and outbound network traffic. The SSL certificate allowed the application to decrypt outgoing traffic to analyse it. Once the new SSL certificate was installed, the application alerted Equifax's employees to suspicious network activity. The certificate had been expired for nine months.
By July 30, Equifax shut off the exploit. At least 34 servers in twenty different countries were used at different points during the breach, making tracking the perpetrators difficult. While the failure to update Struts was a key failure, analysis of the breach found further faults in Equifax' system that made it easy for the breach to occur, including the insecure network design which lacked sufficient segmentation, potentially inadequate encryption of personally identifiable information (PII), and ineffective breach detection mechanisms.
Disclosure and short-term responses.
On September 7, 2017, Equifax disclosed the breach and its scope: affecting over 140 million Americans. "VentureBeat" called the exposure of data on 140+ million customers "one of the biggest data breaches in history." Equifax shares dropped 13% in early trading the day after the breach was made public. Numerous media outlets advised consumers to request a credit freeze to reduce the impact of the breach.
On September 10, 2017, three days after Equifax revealed the breach, Congressman Barry Loudermilk (R-GA), who had been given two thousand dollars in campaign funding from Equifax, introduced a bill to the U.S. House of Representatives that would reduce consumer protections in relation to the nation's credit bureaus, including capping potential damages in a class action suit to $500,000 regardless of class size or amount of loss. The bill would also eliminate all punitive damages. Following criticism by consumer advocates, Loudermilk agreed to delay consideration of the bill "pending a full and complete investigation into the Equifax breach".
On September 15, Equifax released a statement announcing the immediate departures and replacements of its chief information officer and chief security officer. The statement included bullet-point details of the intrusion, its potential consequences for consumers, and the company's response. The company said it had hired cybersecurity firm Mandiant on August 2 to investigate the intrusion internally. The statement did not specify when U.S. government authorities were notified of the breach, although it did assert "the company continues to work closely with the FBI in its investigation".
On September 26 Equifax announced the retirement of CEO Richard Smith, 57, who agreed to remain as an unpaid advisor to assist in the transition to a new CEO.
On September 28, new Equifax CEO Paulino do Rego Barros Jr. responded to criticism of Equifax by promising that the company would, from early 2018, allow "all consumers the option of controlling access to their personal credit data", and that this service would be "offered free, for life".
On October 26, Equifax appointed technology executive Scott A. McGregor to its board of directors. In announcing the change, the board's chairman noted McGregor's "extensive data security, cybersecurity, information technology and risk management experience". "The Wall Street Journal" reported that he joined the board's technology committee, which has duties that include oversight of cybersecurity.
Aftermath.
Since the initial disclosure in September 2017, Equifax expanded the number of records they discovered were accessed. In both October 2017 and March 2018, Equifax reported that an additional 2.5 and 2.4 million American consumer records were accessed, respectively, bringing the total to 147.9 million. Equifax narrowed its estimate for UK consumers affected by the breach to 15.2 million in October 2017, of which 693,665 had sensitive personal data disclosed. Equifax also estimated that the number of drivers' licenses breached in the attack to be 10-11 million.
Security experts expected that the lucrative private data from the breach would be turned around and sold on black markets and the dark web, though as of May 2021, there has been no sign of any sale of this data. Because the data did not immediately show up in the first 17 months following the breach, security experts theorized that either the hackers behind the breach were waiting for a significant amount of time before selling the information since it would be too "hot" to sell that close to the breach, or that a nation-state was behind the breach and planning on using the data in a non-financial manner such as for espionage.
Litigation and fines.
Numerous lawsuits were filed against Equifax in the days after the disclosure of the breach. In one suit the law firm Geragos &amp; Geragos has indicated they would seek up to $70 billion in damages, which would make it the largest class-action suit in U.S. history. Since October 2017, hundreds of consumers have sued Equifax for the data breach, some winning small claims cases in excess of $9,000, including actual damages, future damages, anxiety, monitoring fees and punitive damages.
In September 2017, Richard Cordray, then director of the Consumer Financial Protection Bureau (CFPB), authorized an investigation into the data breach on behalf of affected consumers. However, in November 2017, Mick Mulvaney, President Donald Trump's budget chief, who was appointed by Trump to replace Cordray, was reported by Reuters to have "pulled back" on the probe, along with shelving Cordray's plans for on-the-ground tests of how Equifax protects data. The CFPB also rebuffed bank regulators at the Federal Reserve Bank, Federal Deposit Insurance Corporation and Office of the Comptroller of the Currency who offered to assist with on-site exams of credit bureaus. Senator Elizabeth Warren, who released a report on the Equifax breach in February 2018, criticized Mulvaney's actions, stating: "We're unveiling this report while Mick Mulvaney is killing the consumer agency's probe into the Equifax breach. Mick Mulvaney shoots another middle finger at consumers."
On July 22, 2019, Equifax agreed to a settlement with the Federal Trade Commission (FTC), CFPB, 48 U.S. states, Washington, D.C., and Puerto Rico to alleviate damages to affected individuals and make organizational changes to avoid similar breaches in the future. The total cost of the settlement included $300 million to a fund for victim compensation, $175 million to the states and territories in the agreement, and $100 million to the CFPB in fines. In July 2019, the FTC published information on how affected individuals could file a claim against the victim compensation fund using the website EquifaxBreachSettlement.com.
In the UK, the Financial Conduct Authority imposed a financial penalty of £11,164,400 for failing to protect the information of UK consumers.
Perpetrators.
The United States Department of Justice announced on February 10, 2020 that they had indicted four members of China's military on nine charges related to the hack, though there has been no additional evidence that China has since used the data from the hack. The Chinese government denied that the four accused had any involvement with the hack.
Criticism.
Following the announcement of the May–July 2017 breach, Equifax's actions received widespread criticism. Equifax did not immediately disclose whether PINs and other sensitive information were compromised, nor did it explain the delay between its discovery of the breach in July and its public announcement in early September. Equifax stated that the delay was due to the time needed to determine the scope of the intrusion and the large amount of personal data involved.
It was also revealed that three Equifax executives sold almost $1.8 million of their personal holdings of company shares days after Equifax discovered the breach but more than a month before the breach was made public. The company said the executives, including the chief financial officer John Gamble, "had no knowledge that an intrusion had occurred at the time they sold their shares". On September 18, "Bloomberg" reported that the U.S. Justice Department had opened an investigation to determine whether or not insider trading laws had been violated. "As Bloomberg notes, these transactions were not pre-scheduled trades and they took place on August 2, three days after the company learned of the hack".
When publicly revealing the intrusion to its systems, Equifax offered a website ([URL] for consumers to learn whether they were victims of the breach. Security experts quickly noted that the website had many traits in common with a phishing website: it was not hosted on a domain registered to Equifax, it had a flawed TLS implementation, and it ran on WordPress which is not generally considered suitable for high-security applications. These issues led Open DNS to classify it as a phishing site and block access. Moreover, members of the public wanting to use the Equifax website to learn if their data had been compromised had to provide a last name and six digits of their social security number.
The website set up to check whether a person's personal data had been breached (trustedidpremier.com) was determined by security experts and others to return apparently random results instead of accurate information. As with [URL] this website, too, was registered and constructed like a phishing website, and it was flagged as such by several web browsers.
The Trusted ID Premier website contained terms of use, dated September 6, 2017 (the day before Equifax announced the security breach) which included an arbitration clause with a class action waiver. Attorneys said that the arbitration clause was ambiguous and that it could require consumers who accepted it to arbitrate claims related to the cybersecurity incident. According to Polly Mosendz and Shahien Nasiripour, "some fear[ed] that simply using an Equifax website to check whether their information was compromised bound them to arbitration". The equifax.com website has separate terms of use with an arbitration clause and class action waiver, but, according to Brian Fung of "The