Reread the following passage from the article.

“Like a good water filter, the firewall is present solely to keep the bad out. Thus, it is absolutely necessary for any computer that has access to the Internet. Using the water metaphor, you can imagine the Internet is a lake or an ocean, and the firewall is the filter that makes that water drinkable.”

Extending the water metaphor above, where would antivirus software and the individual’s own attention to security fit?
Write your answer in no more than three complete sentences, using at least two details from the text to support your answer.