$[$Protection and Security: $15\%]$

$(1)$ Please give three methods to implement a protection domain and explain when domain switching will occur in each method. $(3\%)$

$(2)$ Please list the advantages of using language$-$based protection. $(4\%)$

$(3)$ What is the difference between a computer virus and a computer worm? $(4\%)$

$(4)$ In asymmetric encryption, how do you realize key distribution? $(2\%)$

$(5)$ What is the difference between signature$-$based and anomaly detection? $(2\%)$