A Hungarian citizen has pleaded guilty to stealing confidential information from the computers of Marriott International, and threatening to reveal the information if the hotel chain did not offer him a job maintaining the company's computers, the Department of Justice said.

Attila Nemeth, 26, pleaded guilty in a US court, according to a statement by DOJ. He was detained after he travelled to the states on a ticket purchased by Marriott for a fictitious job interview.

Nemeth is said to have admitted that he used an infected email attachment sent to some Marriott employees to install malicious software on the company's system that gave him a "backdoor" access to proprietary email and other files.

Nemeth sent an email to Marriott staff on November 11 last year, informing them that he had been accessing Marriott's computers for months and had obtained proprietary information, according to Nemeth's plea agreement. He threatened to reveal the information if Marriott did not give him a job maintaining the company's computers.

As he had not received a response from Marriott, Nemeth sent another mail on November 13 containing eight attachments, seven of which were documents stored on Marriott's computers. The documents included financial documentation and other confidential and proprietary information, the DOJ said.

A US Secret Service agent, using the identity of a fictitious employee of Marriott, communicated with Nemeth on November 18, who continued to call and email the undercover agent demanding a job to prevent the public release of the documents, according to the plea agreement. Nemeth emailed a copy of his Hungarian passport as identification and offered to travel to America, according to the DOJ.

On January 17 this year Nemeth arrived at Washington Dulles Airport on a ticket purchased by Marriott, for a mock employment interview. The interview was conducted by a Secret Service agent who assumed the role of the Marriott employee with whom Nemeth thought he had been communicating.

During the interview, Nemeth is said to have demonstrated how he accessed the Marriott network, his continued ability to access the Marriott network, and the location of the stolen Marriott proprietary data on a computer server located in Hungary.

Nemeth faces a maximum penalty of 10 years in prison for the transmission of the malicious code and a maximum of five years in prison for threatening to expose confidential and proprietary information if Marriott did not give him a job, DOJ said.

The loss to Marriott as a result of the intentional damage caused by Nemeth is said to be between $400,000 (£257,000) and $1 million dollars in salaries, consultant expenses and other costs associated with the intrusion.

Nemeth remains detained. Sentencing is scheduled for February 3 next year.