The Purdue Model and OT Network Segmentation Explained: Levels, Zones and Conduits
Purdue levels 0 to 5 and the OT DMZ, how ISA/IEC 62443 zones and conduits relate to them, and what NIST SP 800-82 Rev. 3 says about segmentation.
Plain-English explainers for the concepts that come up across exams. All guides
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- Access Control Models: DAC, MAC, RBAC and ABAC ComparedHow discretionary, mandatory, role-based, rule-based and attribute-based access control decide who gets in, plus least privilege and separation of duties.Updated 1 Nov 2026
- Amazon S3 Storage Classes Compared: Which One WhenEight Amazon S3 storage classes side by side: Availability Zones, minimum storage durations, minimum billable sizes and Glacier retrieval times.Updated 1 Nov 2026
- Azure RBAC vs Microsoft Entra ID Roles: The Difference That Trips People UpAzure roles control Azure resources, Microsoft Entra roles control the directory. Scopes, built-in roles, custom roles and elevated access explained.Updated 1 Nov 2026
- Business Continuity vs Disaster Recovery: How Security Exams Separate ThemBCP versus DRP scope in NIST SP 800-34 Rev. 1, the three-step business impact analysis, MTD, RTO and RPO, test types, and who owns each plan.Updated 1 Nov 2026
- CVSS Scores Explained: Metrics, Severity Ratings and What Changed in v4.0CVSS v3.1 base metrics, severity bands, vector strings and a worked score, plus what FIRST changed in CVSS v4.0.Updated 1 Nov 2026
- Data States and Data Classification Levels for Security ExamsData at rest, in transit and in use, US classification levels, the SY0-701 labels and data roles, as NIST, the exam objectives and the EDPB define them.Updated 1 Nov 2026
- Incident Response Steps in Order: The Sequence Security Exams TestThe Security+ incident response order, NIST SP 800-61 Rev. 2 and Rev. 3, and the SANS six steps compared, with the ordering traps to avoid.Updated 1 Nov 2026
- Kubernetes Objects Explained: Pods, Deployments, Services and MoreWhat each core Kubernetes object does, per the kubernetes.io docs: workloads, Service types, ConfigMaps, Secrets, Namespaces, volumes and Ingress.Updated 1 Nov 2026
- Linux File Permissions and chmod: Octal, Symbolic and Special BitsHow rwx works on files and directories, octal and symbolic chmod, chown and chgrp, umask masking, and SUID, SGID and sticky bits in ls -l.Updated 1 Nov 2026
- Nmap Scan Types and Flags for PenTest+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.Updated 1 Nov 2026
- Phishing, Vishing, Smishing and Other Social Engineering Attacks ComparedClear definitions and the one clue that separates phishing, vishing, smishing, whaling, BEC, pretexting, typosquatting, tailgating and more.Updated 1 Nov 2026
- Ports and Protocols to Memorise for Security+ and Network+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.Updated 1 Nov 2026
- Risk Formulas for CISSP and Security+: SLE, ALE and ARO With Worked ExamplesLearn 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.Updated 1 Nov 2026
- RTO and RPO Explained: High Availability vs Disaster RecoveryRTO, RPO, MTD, MTTR and MTBF defined from NIST and AWS, why high availability is not disaster recovery, and how to pick a DR strategy.Updated 1 Nov 2026
- Security Frameworks Compared: NIST CSF 2.0, ISO 27001 and CIS ControlsWhat 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.Updated 1 Nov 2026
- Subnetting Without a Calculator: A Method for CCNA and Network+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.Updated 1 Nov 2026
- Symmetric vs Asymmetric Encryption, Hashing and Salting ExplainedWhat encryption, hashing and salting each do, which algorithms belong where, how key exchange and signatures work, and which algorithms are retired.Updated 1 Nov 2026
- The AWS Shared Responsibility Model: Who Secures WhatHow AWS splits security of the cloud from security in the cloud, and how your share changes across EC2, RDS, Lambda and S3.Updated 1 Nov 2026
- The OSI Model Layer by Layer, With Exam-Style ExamplesWhat 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.Updated 1 Nov 2026
- The Purdue Model and OT Network Segmentation Explained: Levels, Zones and ConduitsPurdue levels 0 to 5 and the OT DMZ, how ISA/IEC 62443 zones and conduits relate to them, and what NIST SP 800-82 Rev. 3 says about segmentation.Updated 1 Nov 2026
- The Security+ SY0-701 Acronym List: Which Ones to Learn FirstA plain-English guide to CompTIA's SY0-701 acronym list: the groups to learn first, NIST meanings, repeated letters and spellings to watch.Updated 1 Nov 2026
Category Study topics
Subnetting Without a Calculator: A Method for CCNA and Network+
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.
Phishing, Vishing, Smishing and Other Social Engineering Attacks Compared
Clear definitions and the one clue that separates phishing, vishing, smishing, whaling, BEC, pretexting, typosquatting, tailgating and more.
The Security+ SY0-701 Acronym List: Which Ones to Learn First
A plain-English guide to CompTIA's SY0-701 acronym list: the groups to learn first, NIST meanings, repeated letters and spellings to watch.
Security Frameworks Compared: NIST CSF 2.0, ISO 27001 and CIS Controls
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.
Amazon S3 Storage Classes Compared: Which One When
Eight Amazon S3 storage classes side by side: Availability Zones, minimum storage durations, minimum billable sizes and Glacier retrieval times.
RTO and RPO Explained: High Availability vs Disaster Recovery
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.
Risk Formulas for CISSP and Security+: SLE, ALE and ARO With Worked Examples
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.
Ports and Protocols to Memorise for Security+ and Network+
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.
The OSI Model Layer by Layer, With Exam-Style Examples
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.
Nmap Scan Types and Flags for PenTest+
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.
Linux File Permissions and chmod: Octal, Symbolic and Special Bits
How rwx works on files and directories, octal and symbolic chmod, chown and chgrp, umask masking, and SUID, SGID and sticky bits in ls -l.