Which device is commonly used to shield private networks from external attacks?

• A. Firewall
• B. Antivirus
• C. Digital signature
• D. Formatting

Answer: (A)

Protecting a private network from external threats relies on controlling access at the network edge. The device that does this by inspecting traffic and enforcing rules is a firewall. It sits between the internal network and the internet (or other untrusted networks) and decides which packets and sessions are allowed to pass based on criteria like IP addresses, ports, protocols, and sometimes more advanced inspection. This creates a barrier that blocks many unauthorized or dangerous requests before they reach internal devices, reducing the risk from external attacks. Antivirus programs run on individual devices to detect malware already on a device; they don’t shield the entire network from external traffic. A digital signature is about confirming who sent data and that it hasn’t been altered; it doesn’t filter traffic or block intrusion. Formatting is simply changing the layout or structure of data and has nothing to do with network protection.