Final answer:
A firewall is the mechanism used to protect private networks from outside attacks by controlling incoming and outgoing network traffic. Alongside a firewall, two-factor authentication and stronger passwords significantly enhance security.
Step-by-step explanation:
The mechanism to protect private networks from outside attack is A.Firewall.
The function of a firewall is to serve as a barrier between your internal network and incoming traffic from external sources (such as the internet) to block malicious traffic like viruses and hackers.
A firewall can be software-based or hardware-based and is used to help keep a network secure. Its primary objective is to control the incoming and outgoing network traffic by analyzing data packets and determining whether they should be allowed through or not, based on a predetermined rule set.
Increased security measures such as two-factor authentication, using stronger passwords, and education to avoid getting scammed are also vital for protecting individual users and organizations from cyber threats.