A person writes a malicious computer program and embeds it in an email. When someone receives the email, the program makes copies of itself on their hard drive, and also sends new emails with the program to other recipients. However, if a user has installed security software, it blocks the email. Match the features of the computer "virus" to the similar features of a biological virus.

$1$

Computer

$2$

$3$

Email

Match each of the options above to the items below.

Viral capsid

Host cell

Viral genome

Immune system