Sarathi is not just a font; it is a standalone application. Its primary purpose is to provide a platform where users can type in Tamil without needing to install complex system-level language packs.
If you are looking for a legal, virus-free Tamil typing experience, consider these free and open-source alternatives that offer similar "Sarathi-style" phonetic typing:
Fix: Run the software as Administrator. Go to Settings > Privacy & Security > Windows Security > App & Browser Control > Turn off "Reputation-based protection" temporarily while using Sarathi.