A transit hack resulted in passengers getting free rides on San Francisco's light-rail trains after ticket machines had to be taken offline over the weekend.
Passengers enjoyed the Muni Metro freebies Friday night and all day Saturday, reported the San Francisco Chronicle, as San Francisco Municipal Transportation Agency officials struggled to get the systems running again.
Forbes reported on Monday that the railway's systems were back online.
A message on the computer screens of Muni Metro agents read "You Hacked, ALL Data Encrypted," when the ticket machines went offline, said the Chronicle. The agency said it allowed all customers to ride free as a precaution and transit service was not disrupted.
"We are focused now on working to investigate the matter fully to find out all other details," said Muni Metro spokesman Paul Rose. "But at this point there is no impact to transit service, to our security systems or to our customers' private information."
Sources told KPIX-TV on Saturday that the transit system had been "hacked for days."
Rose declined to give more information. "Because this is an ongoing investigation it would not be appropriate to provide additional details at this point," he said.
Transportation officials said the hack might prevent workers at the agency from getting paid this week.
Silicon Valley venture capitalist and early-stage security investor Mahendra Ramsinghani told the Chronicle that the hack could have been a ransomware attack, a type of malware preventing users from accessing their own computer system until a "ransom" is paid to release the data.
The website Hoodline reported that a "pseudonymous hacker" said the hackers wanted $73,000 to release more than 2,000 computers in the SFMTA network.
"The severity of the attack still remains unknown to the public. However, documents released by one of the hackers suggest many vital agency functions have been compromised, including payroll, email servers, Quickbooks, NextBus operations, various MySQL database servers, staff training and personal computers for hundreds of employees," said Kevin Montgomery of Hoodline on Sunday.