Security Experts:

Users File Lawsuit Against Yahoo Over Data Breach

Several class actions have been filed against Yahoo in California and Illinois over the recently disclosed data breach that affected at least 500 million accounts.

Plaintiffs are mainly displeased with the fact that Yahoo has failed to protect their personal information, but they also pointed to how long it took the company to detect and disclose the attack. Some of them believe their details had already been misused by cybercriminals before Yahoo confirmed the breach.

In one of the California lawsuits, the plaintiffs referenced a Ponemon Institute study which estimates that the average time to detect an attack is 191 days. They highlighted in the complaint that it took Yahoo nearly two years, which they believe is an “unusually long period of time.”

Yahoo revealed last week that hackers likely sponsored by a nation state breached its systems in late 2014. The company said the attackers accessed names, email addresses, phone numbers, dates of birth, bcrypt-hashed passwords and, in some cases, encrypted or unencrypted security questions and answers.

According to some reports, Yahoo discovered this breach while conducting an investigation into claims that someone had stolen 200 million user accounts in 2012. Yahoo reportedly launched the investigation in July, but it failed to inform Verizon, which has agreed to buy the company’s core business for $4.8 billion.

Yahoo stock surged after the Verizon acquisition announcement, but it dropped from $44.83 to $42.42 following news of the massive breach.

The company has not shared any information on which country might be behind the attack. Experts have speculated that it could be any one of the United States’ biggest cyberspace “enemies,” including Russia, China or North Korea.

Yahoo’s weak security controls

The users who filed lawsuits against Yahoo allege that the company misrepresented the safety of its systems and services, and the findings of security experts seem to back these claims, particularly when it comes to cryptographic controls.

Venafi, a company that specializes in securing cryptographic keys and digital certificates, conducted an analysis of external Yahoo websites and discovered several problems. Researchers determined that more than a quarter of the certificates on the company’s sites have not been reissued since January 2015. Venafi pointed out that replacing certificates after a massive breach is critical to prevent attackers from accessing encrypted communications.

Another problem is that many of the certificates use MD5 and SHA-1 cryptographic hashing functions, which are no longer considered secure.

Related: UK Man Involved in 2012 Yahoo Hack Sentenced to Prison

Related: Yahoo Pressed to Explain Huge 'State Sponsored' Hack

Related: Russia? China? Who Hacked Yahoo, and Why?

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.