A Chinese teen has been arrested following his creation of a new malware strain called the Heart App, which has reportedly infected at least 100,000 phones.

The 19-year-old software engineering student identified as “Li,” created the malware to show off his coding chops during his summer vacation, according to a Sophos blog post. Heart App spreads through infected phone owners’ contact lists. When users download the phony app, it sends out a text to their first 99 listed contacts that encourages them to download it, too.

The app launches with a well-designed splash screen that prompts users to create logins. At this point, victims willingly hand over personal information, including their identity card number.

Chinese phone providers have already blocked more than 20 million infected messages.