Yahoo: One billion accounts compromised in second major hack

Security? We've heard of it, claims Yahoo

Accident-prone internet company Yahoo has admitted to another historic hack - going back to August 2013 - which, it warns, has compromised as many as one billion accounts.

The admission means that Yahoo now holds the uncoveted title of the biggest hack in history. The company claims that it only uncovered the attack as a result of its investigation into the 2014 hack, which the company claims put 500 million of its users' accounts at risk, including accounts of BT customers.

However, while the figures for compromised credentials are high, there has been very little evidence of them being used for malevolent purposes, raising questions over who hacked the company and why.

Yahoo says "this incident is likely distinct from the incident we disclosed on September 22, 2016," and said that while it's been working with law enforcement and a third-party cybersecurity firm to trace its origin, it doesn't yet know who the perpetrator was.

"As we previously disclosed in November, law enforcement provided us with data files that a third party claimed was Yahoo user data," Yahoo's chief information security officer Bob Lord said in a statement.

"We analysed this data with the assistance of outside forensic experts and found that it appears to be Yahoo user data. Based on further analysis of this data by the forensic experts, we believe an unauthorized third party, in August 2013, stole data associated with more than one billion user accounts."

Stolen user account information may have included names, email addresses, phone numbers, dates of birth, "hashed" passwords and, in some cases, encrypted or unencrypted security questions and answers.

In addition, Lord said the attackers had worked out a way to forge "cookies" that Yahoo places on user computers when they log in that contain a great deal of information about the user, such as whether that the user has already authenticated to the company's servers.

Payment card data and bank account information were not stored in the system believed to be affected and the hackers did not obtain passwords in clear text, the company said.

Among the one billion accounts are more than 150,000 US government and military employees, according to a Bloomberg report, which claims that these accounts belong to current and former White House staff, congressmen and their aides, FBI agents, officials at the National Security Agency, the Central Intelligence Agency, the Office of the Director of National Intelligence, and each branch of the US military.

Yahoo says it is notifying the account holders affected in the breach and that users will be required to change their passwords. However, we'd advise completely deleting your Yahoo account instead.

"As we've said all along, we will evaluate the situation as Yahoo continues its investigation," a Verizon spokesperson said. "We will review the impact of this new development before reaching any final conclusions."