In this instance, you'll need to enter your Yahoo email addresses to see whether your account has been affected.
The site will tell you when the breach occurred and exactly what information was impacted. A confirmation will then appear, click Continue to finish the process.
The US technology company said it believes this latest cyberattack is "distinct" from another online attack the firm reported in September this year.
That attack involved around 500 million accounts and was said to have been carried out by a "state-sponsored actor" in late 2014.
Google, which runs Gmail, said in a statement: “We've never received such a request, but if we did, our response would be simple: 'no way'." Microsoft, another major email provider, said, “We have never engaged in the secret scanning of email traffic like what has been reported today about Yahoo.” Apple, in a statement said, “We have never received a request of this type.
If we were to receive one, we would oppose it in court.” It was unclear which intelligence agency directed Yahoo to scan emails, the person familiar with the matter said.
Those with a Yahoo email account should be on the lookout for any suspicious-looking messages asking you to input any personal data from your account.
Earlier this year, cybercriminals took advantage of the online attack to try and trick Yahoo mail users into clicking onto phishing websites – mistakenly thinking it was a genuine URL from Yahoo looking to help secure online accounts.
Run by security researcher Troy Hunt – the free database tracks online breaches and allows anyone to check whether their email address has been included in a publicly-available leak.
Instead of looping in the security team, Mayer turned to the Yahoo’s email engineers to develop the software, Reuters reported.
That decision led to a programming error that left all Yahoo email vulnerable to hackers, the former Yahoo employee said.
The company’s decision not to fight the order from intelligence officials caused Yahoo’s then-chief information security officer Alex Stamos to resign last year — and at least one other security staffer left the company — due to ethical concerns about the surveillance program, according to the person, who spoke on the condition of anonymity because the matter was confidential.
Reuters, citing unnamed former employees, first reported the news Tuesday.
You can also sign-up for alerts tied to any of your email addresses, so you will be notified as soon as another breach is picked up by the site. Yahoo provides email accounts for a number of partners, including BT, Sky UK, Verizon, AT&T, Frontier, Rogers, Spark, and MTS.