Twilio hack exposed Signal phone numbers of 1,900 users. Phone numbers of close to 1,900 Signal users were exposed in the data breach Twilio cloud communications company suffered at the beginning of the month. Twilio provides phone number verification services for Signal and last week disclosed that an attacker hacked its network on August 4. The communications company confirmed that data belonging to 125 of its customers was exposed after the hackers gained access to Twilio employee accounts by sending them text messages with malicious links. Third-party company: Twilio.