The Egyptian State Security Investigations Service (SSI) (Arabic: , Transliteration: ) was the highest national internal security authority in Egypt. Estimated to employ 100,000 people, the SSI was the main security and intelligence apparatus of Egypt's Ministry of Interior. The SSI focused on monitoring underground networks of radical Islamists and probably planted agents in those organizations and had the role of controlling opposition groups, both armed groups and those engaged in peaceful opposition to the government.