Transport for London, the government body that oversees public transport in the British capital, said it was experiencing online outages due to an “ongoing cyber security incident” that is expected to last into the weekend.
TfL, which runs the London Underground (Tube) and buses and trams across London, said that while public transport in the city was “operating as normal”, some customer-facing systems were offline, including some ticketing systems and online real-time tube arrival information.
Details of the incident are unclear. TfL disclosed the cyber attack on September 2 and said it had taken steps to “prevent further access to our systems”.
TfL issued a short update on its website on Friday saying there was no evidence yet that customer data had been compromised in the cyber attack.
TfL spokesperson Princess Mills declined to answer TechCrunch's specific questions about the incident, including what logs or other evidence the company has that could determine whether data was stolen. TfL also declined to make its executives overseeing cybersecurity available for an interview.
In a brief statement from TfL's chief technology officer Shashi Verma, the transport network confirmed that it “identified suspicious activity on Sunday and took steps to restrict access.”
According to its cyber incident page as of Friday, TfL said: “A number of staff have restricted access to systems and emails and as a result responses to enquiries and previously submitted web forms may be delayed or unavailable.”
Sources told BBC News that TfL staff have been told to work from home as many of its back-office systems at headquarters have been affected.
A TechCrunch review of TfL's public web infrastructure found that many of the organization's systems are not online or have limited access to the public internet, likely a measure to isolate intruders and prevent further access.
At the time of writing, TechCrunch discovered that several TfL systems, including the employee log-on portal, were still accessible from the internet.
Post-publication comments from TfL have been updated.