The least expensive option that Marcus has is to build a firewall that would help to prevent attacks from the hackers.
This is also known as a security device. This device would help to safe guard Marcus's computer by filtering the traffic and also blocking any form of public internet.
This option would be the most viable thing for him to do as he continues to carry out this research.
Read more on internet firewall here:
https://brainly.com/question/13693641