WASHINGTON — Former Yahoo CEO Marissa Mayer told lawmakers Wednesday that the threat from state-sponsored hackers has changed the playing field so dramatically that even the best-defended companies can fall victim.
Mayer joined former and current CEOs of Equifax in testifying before a Senate committee examining recent data breaches that affected millions of Americans. Lawmakers said they hoped to use the information learned to shape future legislation.
In Yahoo’s case, stolen information for billions of users included names, e-mail addresses, phone numbers, birthdates, and security questions and answers. Mayer said the thefts occurred during her nearly five-year tenure and she wants to ‘‘sincerely apologize to each and every one of our users.’’
‘‘As we all have witnessed: no company, individual, or even government agency is immune from these threats,’’ Mayer said.
Mayer said Yahoo successfully defended itself against a barrage of state-sponsored and private hacks over the years and even employed hackers to test the company’s defenses. In the end, she said ‘‘Russian agents intruded on our systems and stole our users’ data.’’
Mayer is part of a long line of company executives and former executives who have made their way to Capitol Hill in recent years to explain how their company fell victim to a cyberattack. She was joined by the interim CEO of Equifax, Paulino Barros Jr., who took over after hackers exposed the personal information of 145 million Americans.
Barros told the committee he has focused on improving customer service and revising the company’s structure so that the company’s chief security officer reports directly to him. He also said the company is on schedule to release a computer app in January that will allow consumers to lock and unlock their credit data.
Senator John Thune, a South Dakota Republican, the committee chairman, said 48 states have separate laws governing how and when companies must notify consumers of a breach. He said a federal law should replace those state laws.
‘‘A single federal standard would ensure all consumers are treated the same with regard to notification of data breaches that might cause them harm,’’ Thune said.
Senator Bill Nelson, a Florida Democrat, said lawmakers need to have the political will to hold corporations more accountable for breaches.
‘‘Only stiffer enforcement and stringent penalties will help incentivize companies to properly safeguard consumer information and promptly notify them when their data has been compromised,’’ Nelson said.
Some of the most pointed questioning came from Thune when he asked Mayer how the company for so long failed to recognize that data for all 3 billion of its user accounts were compromised. She said Yahoo still has not been able to identify the intrusion that led to that theft.
‘‘We don’t exactly understand how the act was perpetrated,’’ which explains why there are some gaps in information, she said.