Westminster Bridge attacker Khalid Masood sent a WhatsApp message that cannot be accessed because it was encrypted by the popular messaging service, a top British security official said Sunday. British press reports suggest Masood used the messaging service just minutes before a rampage Wednesday that left three pedestrians and one police officer dead and dozens more wounded. Home Secretary Amber Rudd used appearances on BBC and Sky News to urge WhatsApp and other encrypted services to make their platforms accessible to intel services and police trying to carrying out lawful eavesdropping. "We need to make sure that organizations like WhatsApp—and there are plenty of others like that—don't provide a secret place for terrorists to communicate with each other," she said, per the AP.
Rudd did not provide any details about Masood's use of WhatsApp, saying only "this terrorist sent a WhatsApp message and it can't be accessed." But her call for a "back door" system to allow authorities to retrieve information is likely to meet resistance from the tech industry. Police are trying to pinpoint Masood's motive and identify any accomplices, making the WhatsApp message a potential clue to his state of mind and his social media contacts. Rudd said attacks like Masood's would be easier to prevent if authorities could penetrate encrypted services after obtaining warrants. British police say they still believe Masood, a 52-year-old Briton, acted alone and say they have no indications that further attacks are planned. But of his motives, "that understanding may have died with him," said a Metropolitan Police rep. (Read more Khalid Masood stories.)