The Guardian's jobs website has been hacked, with half a million user accounts affected.
In a statement on its website, the Guardian said the site was now secure, and that the incident had been reported to the Police's central e-crime unit.
The half-million affected users were contacted over the weekend. The newspaper company said that no bank or financial details were lost, and that many of the accounts were two years out of date. The American side of the site was not attacked.
"This is apparently a deliberate and sophisticated crime, of which the Guardian is a victim in addition to some of our users," the statement said.
"It is clear that only a minority of Guardian Jobs users are at risk," the site said.
"The police remain anxious to keep information about the apparent theft to a minimum, in order not to compromise their investigations, but did agree with us that we could inform those users who may be affected," it added. "We stress our regret that this breach has occurred."
Security firm Finjan said data that can be used to assemble "identity theft kits" is seen as valuable to online criminals.
"Although top web sites have been - and continue to be - targeted by cybercriminals, those sites that store identity information will continue to a primary target, especially now that criminal hackers are being affected by the economic situation we all find ourselves in," said Yuval Ben Itzhak, chief technology officer, in a statement.
Click here to find out about the worst hacking attacks - and the punishments the hackers faced.
