Yahoo has announced that it suffered another security breach in 2013.

It is believed that the breach compromised the accounts of over 1 billion users. The company is still struggling to unravel the mystery of its previously announced security breach, which occurred in 2014. These two breaches are one of the biggest known cyber attacks.

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The newly announced breach let hackers collect personal information of Yahoo users. The personal information included names, telephone numbers, email addresses, date of birth, and other such data. In certain cases, it also included encrypted or unencrypted security questions and answers.

According to Bloomberg, the affected users include government and military employees. The number of such employees may exceed 150,000. These employees include former and current White House staff, FBI agents, US congressmen, their aides, the CIA, and the others.

This information was mined by Andrew Komarov, a cyber security researcher. The government was informed about the possible breach, and it took steps to alert Yahoo.

Lonny Anderson, former technology director for the NSA, told Bloomberg that "We went to great lengths to keep the fact people worked at NSA as low-profile as we possibly could. The last thing we'd want is an alpha list of NSA employees."

Yahoo has not identified the culprits behind the cyber attacks yet. The new breach is likely to further dampen Yahoo's acquisition deal with Verizon.  Verizon spokesman Bob Verettoni stated, "We will review the impact of this new development before reaching any final conclusions."

It is not clear whether Yahoo had the knowledge of the breach before the start of its negotiations with Verizon. The company has provided contradictory statements about whether it knew about the 2014 breach. In November, Yahoo reported that some of its employees knew about the breach but did not know about the severity of the situation.