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Free reference pages, cheat sheets, and concept explainers for IT and security students. Everything I wish I had starting out.
Cheat Sheets 7 pages
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Common Ports
Searchable reference for TCP/UDP ports. Protocol, service name, category, and plain-English descriptions. Filterable by protocol and category.
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Common Terms
Definitions for the terms you'll encounter in IT, networking, and cybersecurity. Filterable by category — from CIA Triad to Zero Trust to BGP.
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HTTP Status Codes
Every HTTP status code grouped by class — 1xx through 5xx. What each means, when you'll see it, and what to do about it.
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Linux Commands
The commands you'll actually use — grouped by category: file system, networking, permissions, processes, piping. Filterable and printable.
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Networking Basics
TCP/IP stack, subnetting rules, CIDR quick reference, and the protocols every Network+ candidate needs cold.
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Regex Quick Reference
Character classes, quantifiers, anchors, groups, and lookaheads with live examples. The regex syntax card you'll bookmark and never close.
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Concept Explainers 7 pages
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Firewalls & ACLs
Stateful vs stateless, packet filtering, application-layer firewalls, and how access control lists actually control access. Rule design principles included.
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How DNS Works
From typing a URL to getting a response — recursive resolvers, authoritative servers, TTL, caching, and why DNS is almost always the answer when something breaks.
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How TLS Works
The TLS handshake step by step — certificates, asymmetric vs symmetric encryption, cipher suites, and what actually happens when you see that padlock.
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OSI Model
All seven layers explained — what each one does, which protocols live there, how encapsulation works, and which devices operate at which layer.
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PKI & Certificates
How certificate authorities, chains of trust, and X.509 certs work — signing, revocation, common errors, and what's actually inside a certificate.
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OWASP Top 10
The ten most critical web application security risks — what each one is, real attack examples, and how to prevent them. Essential reading for developers and security teams.
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The CIA Triad
Confidentiality, Integrity, Availability — explained with real-world examples, not textbook definitions. The foundation every security decision is built on.
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