"As CEO, these thefts occurred during my tenure, and I want to sincerely apologize to each and every one of our users", she told the Senate Commerce Committee, which had called on her and on Equifax executives to discuss their recent incidents.
Former top executives at Yahoo and Equifax have apologised again for breaches that exposed billions of customer accounts.
Mayer and Smith were flanked by officials from their former companies, as Congress sought to get to the bottom of how three billion global user accounts at Yahoo and 146 million American Social Security numbers and more at Equifax were stolen by hackers.
"The threat from state sponsored attacks has changed the playing field so dramatically that today I believe all companies, even the most well defended ones, could fall victim to these crimes", she said. Richard Blumenthal of CT says enforcing punishments for data breaches on executives like Mayer could motivate companies to protect users' data.
"Unfortunately, while all our measures helped Yahoo successfully defend against the barrage of attacks by both private and state-sponsored hackers, Russian agents intruded on our systems and stole our users' data".
Mayer volunteered to testify on data breaches, but only after being subpoenaed. But- despite prodding from senators -Equifax CEO Paulino do Rego Barros Jr. did not agree to stop use of controversial artibration agreements, nor did he commit Equifax to doing personalized outreach, free credit monitoring, or extended benefits to veterans.
"Massive data breaches have touched the vast majority of American consumers", said Thune. The government is weighing whether to impose tougher standards on companies, such as requirements for notifying consumers after a breach.
They say new laws may be necessary amid rising cyber attacks that threaten the privacy of personal data. "Not fines, or other penalties - or real deterrents", said Connecticut Sen.
USA lawmakers have been grilling corporate leaders in recent months over failures to protect sensitive information on hundreds of millions of Americans.
Consultants hired by Equifax to investigate haven't been able to identify the attackers, according to a summary of their report provided to Senate staff before Wednesday's hearing and obtained by Bloomberg.