The ransom demand arrived one recent morning by email, after about a dozen guests were locked out of their rooms at the lakeside Alpine hotel in Austria.

The electronic key system at the picturesque Romantik Seehotel Jaegerwirt had been infiltrated, and the hotel was locked out of its own computer system, leaving guests stranded in the lobby, causing confusion and panic.

"Good morning?" the email began, according to the hotel's managing director, Christoph Brandstaetter. It went on to demand a ransom of two bitcoins, or about $1,800, and warned that the cost would double if the hotel did not comply with the demand by the end of the day, Jan. 22.

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Mr. Brandstaetter said the email included details of a "bitcoin wallet" — the account in which to deposit the money — and ended with the words, "Have a nice day!"

With the 111-year-old hotel brimming with eager skiers, hikers and vacationers, some having paid about $530 for a suite with a panoramic view and sauna, Mr. Brandstaetter said he decided to cave in.

Guests had already complained that their electronic room keys were not working, and receptionists' efforts to create new ones had proved futile. Bashing down the doors was not an option.

The reservation system for the hotel in the village of Turracherhohe, about 90 minutes by care from Salzburg, was paralyzed.

"We were at maximum capacity with 180 guests and decided that it was better to give in," he said. "The hackers were very pushy."