Virtual Private Network. Creates an ENCRYPTED tunnel between a remote device and the company network so traffic is private over an untrusted connection.

The traffic inside the VPN is scrambled. Anyone watching on the public network (coffee shop Wi-Fi, ISP, etc.) sees only encrypted data, not the real content.

Network Access Control. Checks WHO is connecting and what kind of DEVICE before allowing it onto the network.

What NAC checks. Examples: is the OS up to date, is antivirus installed and running, is the device on the corporate list.

Multi-Factor Authentication. Requires more than one factor (something you know + something you have, etc.) to log in. Essential for remote access.

Any network you do not control. Public Wi-Fi, hotel networks, home networks. A VPN turns this from "untrusted" to "private enough".

Stacking multiple layers (VPN + NAC + MFA + monitoring) so no single failure exposes the network.