Castellum is a small U.S. federal government IT and technology services company focused primarily on the DoD. Castellum provides cybersecurity, software engineering, electronic warfare, intelligence support, and IT modernization services to defense and civilian agencies. Customers use Castellum to operate and modernize critical national security systems, manage cyber threats, process intelligence data, and maintain complex defense platforms. Castellum sells almost entirely to U.S. federal, state, and local government agencies, winning business through competitive bids, and operating as both a prime contractor and subcontractor depending on the program. Work is largely operational and recurring in nature, supporting continuously active missions rather than one-time projects. Castellum's three largest contracts — all with Navy commands covering cyber engineering, ISR, and C4ISR sensor systems — accounted for 54% of FY25 revenue. The business model is labor-intensive: revenue is driven by headcount billable to government contracts, contract win rates, and task order size. Castellum bills under a mix of cost-plus fixed fee, time and materials, and firm fixed price contracts. Margin improvement depends on spreading overhead across a larger revenue base, which underpins Castellum's acquisition-led growth strategy — the company has completed seven acquisitions since 2019. Castellum also pursues organic growth through a ~$817M opportunity pipeline. With 97% of employees holding security clearances and 58% holding STEM degrees, cleared technical personnel are a key operational asset and a meaningful barrier to entry for new competitors.