TripAdvisor said that hackers had stolen a portion of the online travel site’s e-mail list and warned members of the possibility of receiving junk mail messages.

“This past weekend we discovered that an unauthorized third party had stolen part of TripAdvisor’s member e-mail list,” co-founder and chief executive Steve Kaufer said in a message to members. “We’ve confirmed the source of the vulnerability and shut it down,” Mr Kaufer said.

“Only a portion of all member e-mail addresses were taken, and all member passwords remain secure,” he said, adding that members may receive unsolicited emails, or spam, following the break-in.

“Unfortunately, this sort of data theft is becoming more common across many industries, and we take it extremely seriously,” Mr Kaufer said.

The company has taken it up with law enforcement, he said.

In a statement on the TripAdvisor website, TripAdvisor said it was taking additional security precautions to prevent another incident in the future.