(ShareCast News) - Internet company Yahoo is investigating reports that 200 million of its users' account details have been published on the dark web by a hacker linked to similar breaches at MySpace and LinkedIn.Passwords and usernames have been put on sale for thousands of poundsIt is unclear whether the details thta hve been released are from current accounts, or from old inactive ones. A study carried out by Motherboard intially seemed to suggest that they were active accounts, but further probing showed a high probability of the contrary.The hacker, known as Peace, said the data was from 2012. The information is being sold for 3 bitcoins (£1,360)."Yahoo works hard to keep our users safe, and we always encourage our users to create strong passwords, or give up passwords altogether by using Yahoo Account Key, and use different passwords for different platforms," the company said in a statement.According to a sample of the data, it contains usernames, hashed passwords (created with md5 algorithm), dates of birth, and in some cases back-up email addresses.Yahoo was sold to US telecommunications company Verizon for almost $5bn this month. There had been a lengthy auction process for the purchase of the firm in which Verizon emerged victorious.