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Suppose you work in an anti$-$virus software company. Answer the following questions.

QUESTION $3.$ One day you received a report of a suspicious program. By taking a glance at the following code segment, even though you are not so familiar with the assembly language, you immediately realized that this could be a $\_\_\_($type$)$ virus program since $\_\_\_($reason$).$ Codes in $\_\_\_($lines$)$ could be used as its virus signature.

mov eax, $5$

push ecx

pop ecx

add eax, ebx

swap eax, ebx

swap ebx, eax

call $[$eax$]$

nop