Trust is still the most important currency on the Internet. Web-based malware is more prevalent than ever. If your website becomes labelled as infected by Google, you could soon be out of business. Let me introduce Minesweeper. A new, open source tool developed by Shopify to protect its 100,000+ online stores from web-based malware infections. Minesweeper deals with not only the problem of detecting the malware, but also attributing the infection back to a particular asset. It is designed for speed and scalability. The Minesweeper tool will be open-sourced before the conference and made available via http://shopify.github.io/.