The San Francisco Municipal Railway was hacked and riders were able to enjoy free bus and trolley rides late Friday and all day on Saturday.

SF Muni computer systems handling fares were apparently hacked, so fares were free for all. The machines allowing riders to fill up their fare cards had special signs attached on Saturday, showing "free Muni" and "out of service" messages.

As the San Francisco Examiner reports, SF Muni computers displayed a message saying "You Hacked, ALL Data Encrypted."

Ransomware

The hack apparently involved ransomware, as the message displayed on SF Muni computers also offered an email address where authorities could contact the hackers to obtain a key to unlock the hijacked systems.

In ransomware cases, a computer system is hijacked and locks users out until a ransom is paid.

San Francisco Municipal Transportation Agency (SFMTA) spokesman Paul Rose told the Examiner that the agency was "working to resolve the situation," but did not offer any additional details.

Ongoing Investigation

"At this point there are not any indications of any impacts to customers," Rose said on Sunday. "We're doing a full investigation to find out exactly what we are dealing with."

The Examiner learned from a Muni operator who asked to remain anonymous that the systems had been hacked since Friday afternoon.

"There is an ongoing investigation and it wouldn't be appropriate to provide additional details," Rose further told the Examiner.

It remains unclear for now who is behind the hack or what the perpetrators wanted in exchange for unlocking the systems.

Transit Services Unaffected

The hack did not impact transit services, which means there were no interruptions during the hack — just free rides. Nevertheless, some SFMTA employees told the Examiner that their emails were not working. It's unclear whether this issue extended to the nearly 6,000 people employed by the SFMTA.

Muni subway fare gates were locked in an open position, station operators told the Examiner. The lock did not allow them to close the gates electronically. According to Rose, the fare gats were locked in an open position intentionally, in order to enable the free Muni rides.

In light of the hack, employees were also unsure whether they will still get their paychecks this week, CBS's local San Francisco affiliate reports. The transit agency doesn't know yet who is responsible for the hack, or what they want in return, but it's looking into the matter.

More details will likely surface after the investigation is completed, and we'll keep you up to date as soon as we learn more.