Tesla CEO Elon Musk took on Mark Zuckerberg WhatsApp with a "Use Signal" tweet which led to a massive number of signups for the rival app.

Musk’s tweet comes in protest against the new WhatsApp privacy policy which provides sharing more data with parent company Facebook , rasing security concerns among users.

Musk, through his tweet, apparently implied that WhatsApp users should switch to Signal. His tweet was liked and retweeted thousands of times.

Signal is a well-known privacy-focused messaging app, that is widely used by security experts, privacy researchers, academics, and journalists around the world. The Signal protocol also underpins WhatsApp's end-to-end encryption. The difference between the two is that Signal is open source, while WhatsApp is not.

Verification codes were delayed because of the sudden influx of users on the Signal app. "We are working with carriers to resolve this as quickly as possible. Hang in there," the app tweeted..