In this report the threat from anti-satellite, or ASAT, capabilities is briefly described. ASAT weapons include kinetic weapons such as ballistic missiles or other satellites as well as directed energy weapons in the form of lasers and microwaves. Further antagonistic threats to satellites include intentional interference with the satellite signal through electronic jamming or spoofing, cyber attacks and physical attacks on ground stations. Space systems constitute a part of our critical infrastructures and securing this infrastructure in space is of vital importance. A host of approaches to secure the infrastructure in space is further described, with special emphasis on space situational awareness (SSA). Apart from the vital task of monitoring space debris, SSA capabilities can be used to detect ASAT attacks, to determine the intention of an attack, to verify compliance to treaties and also to deter attacks on space systems. The potential application of the Swedish satellite mission Prisma in the context of SSA, mainly verification, is also presented in the report. Finally, the Swedish approach (as compared to the US and European approaches) to the ASAT threat and to secure the infrastructure in space is discussed.