This weekend, riders of the San Francisco Municipal Railway got an unexpected surprise, being offered a free ride after the system's computerized fare systems were apparently hacked.

San Francisco MUNI Metro Hacked

According to San Francisco Examiner, on Friday afternoon, Nov. 25, the MUNI system had been attacked by hackers. On late Friday and Saturday, MUNI riders were greeted with printed "Metro Free" and "Out of Service" signs on ticket machines. The Verge reports that MUNI first became aware of the intrusion on Friday.

Recode reports that a spokesperson told San Francisco's CBS affiliate that in order to minimize customer impact, the system opened the fare gates. All day on Saturday and Sunday morning, rides were free. On Saturday, sources told San Francisco's CBS affiliate that the system had been hacked for days but the officials did not find out who was behind the attack or what the hackers wanted.

MUNI Spokesman Paul Rose said that the agency was "working to resolve the situation," but did not provide additional details. Later on, after being reached by email, the hacker declared that he was seeking a deal with MUNI to undo the damage.

Previous Similar Threats

According to Security Affairs, Morphus Labs linked in September a hacker to a ransomeware strain called Mamba. The security experts think that the malware employs similar tactics to those demonstrated against MUNI.

This isn't the first time when a California organization has to face such an issue. Hollywood Presbyterian Medical Center discovered earlier this year that hackers are keeping its files hostages for a $3.6 million ransom. In a ransomware attack a malicious file is typically downloaded onto a computer and executed to encrypt the important files stocked on the hard drive. The files will be decrypted once a victim pays the demanded ransom.