How does having one unsecured or obsolete device on a network make the entire network vulnerable?

Question

How does having one unsecured or obsolete device on a network make the entire network vulnerable?

In: 3

Answer 1

A virus enters one device and from that device the virus can spread to every other machine, since the major point of items on a network is being able to share stuff. In a way it is similar to humans and vaccines and why you want most of the population vaccinated to stop the spread.