Network Rail, the group which manages tracks and train hubs, said the Wi-Fi remained offline on Thursday following the incident at 19 stations including London Bridge and London Euston as well as Manchester Piccadilly and Edinburgh Waverley.
Telent said in a statement that no personal data had been affected by the hack, adding the matter was now in the hands of the police.
It said an unauthorised change had been made to the Network Rail landing page, provided by Global Reach, from a legitimate administrator account.
“As a precaution, Telent temporarily suspended all use of Global Reach services while verifying that no other Telent customers were impacted,” it added.
Network Rail said it expected the Wifi service to be restored over the weekend once final security checks were completed.
