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Affected: 33 million user accounts, including email addresses, first and last names and phone numbers.
Cost: The breach could cost the company an estimated $850 million, according to The New York Times.
What happened: In possibly the most publicized attack of the year, more than 30 million accounts on affair-site Ashley Madison, owned by Avid Life Media, were hacked and released to the public. The site claims that full credit card numbers were not taken.