Profile for Foreign agents and spies
Finance: Can be very large- many $Bs/year - but an agent on the ground may have relatively little cash behind them.
Time and Effort: Enormous - hundreds of thousands of full time employees - but the individual on the ground is often very much alone.
Group Size: Large - many thousands for some projects - and yet small intelligence cells tend to operate in country.
Other resources: Huge logistics tail with support ranging from custom trade craft to air strikes and blockades.
You see only the very small tip of the very large iceberg - if you can see it at all. They tend to back off rapidly and try from a different angle when detected.