Indirect Cross contamination - Indirect contamination happens as a result of the transmission of bacteria from one source to another without actual contact between the source and the destination.
This usually happens with a carrier.
Carrier is defined as a vehicle or medium that aid in carry bacteria from one source to another.
Example:
Same knife used for slicing ham after previously having used to cut raw chicken. In this case bacteria are transferred from raw chicken to Ham wherein the knife is being used as a carrier.