How CIDR notation works: how to read a block like 10.0.0.0/24, how many addresses it covers, and why 0.0.0.0/0 in a cloud firewall rule matters.

How a DNS lookup turns a name into an address, and why a forged answer in a resolver’s cache is dangerous.

How the TLS 1.3 handshake works, and why validating the server’s certificate is what stops an attacker in the middle.

How a TCP connection opens: the three-way handshake, how it works, and why attackers abuse it. A 60-second lesson with sources.