Are you a Yahoo user? Do this right now

Any password, username or security question that you've used on your Yahoo account may now be in the hands of hackers, who are likely going to try and use that information on other sites.

Yahoo has said in a statement that no Tumblr accounts were compromised, but if you use Flickr, you should definitely be changing your passwords and looking for trouble.

The Yahoo data breach means "serious questions" must be asked of the internet giant, Information Commissioner Elizabeth Denham has said.

Users should avoid clicking on links or downloading attachments from suspicious emails that claim to be updates from Yahoo or others about the breach.

Later, it was revealed that Yahoo had notified the Irish authorities about the breach on Thursday.

The firm urged anybody who has not changed their password details since 2014 to do so as soon as possible.

Yahoo also is recommending that all users change their passwords if they haven't done so since 2014.

For BellSouth email users: Although Yahoo took over the domain years ago, the company hasn't said if those users are included in the hack.

The attack on the firm's network - which dates back to late 2014 - is the biggest such theft of user data to date.

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These kinds of recommendations are pretty much standard all the time but they become even more important if you've been hacked. They should also rethink their usage of any security questions which are shared with the webmail account, since that information also leaked.

Yahoo said it believes a "state-sponsored actor" was behind the data breach, meaning an individual acting on behalf of a government.

If you have ever had an account with Yahoo, you'll need to keep an eye out for an email from the U.S. firm.

Additionally, the Sunnyvale, CA-based company agreed in late July to sell its core business to Verizon Communications (VZ) for $4.83 billion. It is unclear if this alleged hack is the same as the one announced by Yahoo yesterday (22 September). "Consumers are naturally tired of unsolicited calls, but when the caller knows your date of birth, and possibly the name of your first pet, the success of this form of scam increases dramatically", said Gauda in comments sent to SCMagazine.com "All in all, this breach underscores just how valuable data is". Verizon said it would evaluate what it will do next. That includes banks, credit card companies and hotel and airline loyalty programs.

"The vast number of people affected by this cyber attack is staggering and demonstrates just how severe the consequences of a security hack can be", she said.

"We are notifying potentially affected users by email and posting additional information to our website". Yahoo is one of several places to play fantasy sports, and its offerings include football, baseball, basketball, hockey, auto racing and golf.

The search engine is set to be acquired by United States network operator Verizon but a hack of this magnitude is sure to influence the value of the $4.8 billion (~R65.1 billion) acquisition.

Yahoo didn't comment immediately on how the hack and its aftermath might affect its sale to Verizon.

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