TfL has called in the National Crime Agency as it deals with a cyber attack.
Technology experts are working to establish the damage caused by the breach.
However, TfL say early indications were that customer data had not been compromised and the transport network and services had not been affected.
Customers were informed of the attack in a message on Monday evening.
Shashi Verma, TfL’s Chief Technology Officer, said on Monday: “We have introduced a number of measures to our internal systems to deal with an ongoing cyber security incident. The security of our systems and customer data is very important to us and we will continue to assess the situation throughout and after the incident.
“Although we’ll need to complete our full assessment, at present, there is currently no evidence that any customer data has been compromised. There is currently no impact to TfL services and we are working closely with the National Crime Agency and the National Cyber Security Centre to respond to the incident.”
In the summer a cyber attack led to more than 10,000 NHS appointments being cancelled.
Pathology services provider Synnovis was targeted by Russian gang Qilin on June 3, with hackers reportedly obtaining confidential medical information and blood test results of more than 100,000 patients, the court was told.
The ransomware attack saw appointments cancelled at two London NHS trusts and prompted a warning that parts of the NHS’s IT system are “out of date” and at risk of further hacking.
Meanwhile in July Microsoft has revealed the service outage which affected some of its apps and features on Tuesday was sparked by an attempted attack,
The US technology firm said initial problems on its Azure cloud platform had been triggered by a distributed denial-of-service (DDoS) attack, where ‘bad actors’ try and knock a platform offline by flooding it with traffic until it can no longer cope.
