Yahoo’s ‘cyberfail’ could cut $1 billion from Verizon deal

Thieves seemingly had free rein inside Yahoo’s systems

Marissa Mayer, chief executive of Yahoo: tarnished record following cyber attack

Yahoo can’t help being Yahoo, the technology industry’s most hapless company. And now the market is betting the company’s incompetence might cost shareholders $1 billion or more.

Yahoo’s latest embarrassing stumble was a disclosure last Wednesday that, in 2013, cyber thieves siphoned information from more than one billion Yahoo accounts, including user email addresses, scrambled account passwords and dates of birth.

Criminals could use the information to go after more sensitive personal data ...