Swarm of lawsuits follow Yahoo mass data breach

Yahoo is facing multiple class action lawsuits in the US over the 2014 data breach that saw user information for at least 500 million accounts leaked.

The court cases against Yahoo are listed in a filing with the US Securities and Exchange Commission.

The company said to date, 23 putative consumer class action lawsuits have been filed against it in US and overseas courts.

Plaintiffs claim they were harmed by Yahoo's actions in connection with the hack.

Yahoo said it could suffer losses from the court cases but did not provide an estimate of how much, citing the ongoing investigation into the breach.

It also warned that additional lawsuits and claims related to the 2014 security incident could be brought by users, partners, shareholders and others seeking damages and relief.

Yahoo chief information officer Bob Lord in September said the company believed an unnamed state-sponsored actor was behind the data breach.

The internet company is currently negotiating a A$6.7 billion sale to US telco Verizon.