ShieldFont is an open-source typeface designed to protect creative intellectual property from unauthorized AI training. By utilizing glyph substitution within the source code, the font presents readable text to human users while simultaneously delivering polluted data to automated scrapers. This process effectively poisons data-quality filters and disrupts unauthorized dataset acquisition. Rather than attempting to break AI systems, ShieldFont acts as a tactical speed bump to automated extraction, offering independent creators a practical tool to assert agency and digital consent. The project launched with ShieldFont Optik, developed by Playtype, and invites the global design community to adopt these protective measures for their own creative work.