Work out network, broadcast and host ranges for any IPv4 prefix in your head with the block size method, plus /31, /32, VLSM and IPv6 /64.

Clear definitions and the one clue that separates phishing, vishing, smishing, whaling, BEC, pretexting, typosquatting, tailgating and more.

A plain-English guide to CompTIA's SY0-701 acronym list: the groups to learn first, NIST meanings, repeated letters and spellings to watch.

What NIST CSF 2.0, ISO/IEC 27001:2022, ISO/IEC 27002:2022 and CIS Controls v8.1 are for, how each is structured, and which one can be certified.

Eight Amazon S3 storage classes side by side: Availability Zones, minimum storage durations, minimum billable sizes and Glacier retrieval times.

RTO, RPO, MTD, MTTR and MTBF defined from NIST and AWS, why high availability is not disaster recovery, and how to pick a DR strategy.

Learn what AV, EF, SLE, ARO and ALE mean, how the two formulas connect them, and how to test whether a control is worth its yearly cost.

Every port in CompTIA's N10-009 table, grouped by job, with TCP or UDP, secure and insecure pairs, and the IANA details that trip people up.

What each of the seven OSI layers does per ITU-T X.200, the PDU names, how OSI maps to TCP/IP, and how to use the layers to troubleshoot.

What -sS, -sT, -sU, -sV, -O, -A, -Pn, -sn, -T0 to -T5 and the output flags do, and which need root, per the official Nmap reference guide.