Thousands of customer accounts on the National Lottery website may have been compromised in an attempted hack.
Suspicious activity was detected on 26,500 National Lottery online accounts on Monday, operator Camelot said.
But it said that fewer than 50 accounts have had activity take place since the hack with personal information accessed and changed in some cases.
All of the affected accounts have been re-set and players have been contacted to re-activate their accounts, the operator said.
Camelot said there has been no unauthorised access to core National Lottery systems or any of its databases, which would affect draws or payment of prizes.
"In addition, no money has been deposited or withdrawn from affected player accounts," the statement added.
Of our 9.5 million registered online players, we believe that around 26,500 players' accounts were accessed.
A much smaller number - fewer than 50 - have had some activity take place within the account since it was accessed. This was limited to some of their personal details being changed - and some of these details may have been changed by the players themselves.
We have taken the measure of suspending the accounts of these players and are in the process of contacting them to help them re-activate their accounts securely.
In addition, we have instigated a compulsory password reset on the accounts of the 26,500 affected players.
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