Cybersecurity cheat sheet (Penetration testing)

1. 1Security foundationsThe ideas every security role shares: what security protects, how risk is judged, the networking and access basics, cryptography as concepts, and the law on testing.12 concepts

   1. 1CIA triadThe three properties security protects: confidentiality (only the right people can read it), integrity (nobody can change it unnoticed) and availability (it…
   2. 2Risk, threat and vulnerabilityA vulnerability is a weakness, a threat is someone or something that could exploit it, and risk combines how likely that is with how bad the outcome would be.
   3. 3CVSSAn open standard from FIRST that scores a vulnerability from 0 to 10 using factors such as how it is reached, the privileges needed and its impact.
   4. 4Defence in depthUsing several independent layers of control, such as MFA, patching, network rules, monitoring and backups, so one failure does not mean a breach.
   5. 5Least privilegeGiving each person, service and process only the access it needs to do its job, and only for as long as it needs it.
   6. 6Networking basics for securityIP addresses and subnets, TCP and UDP, ports, DNS, HTTP and HTTPS, and what firewalls and proxies do: the path every connection takes.
   7. 7TLSThe protocol that encrypts and authenticates connections such as HTTPS.
   8. 8Authentication and authorisationAuthentication proves who you are; authorisation decides what you are allowed to do once the system knows who you are.
   9. 9Multi-factor authenticationRequiring two or more kinds of proof to sign in: something you know, something you have or something you are.
   10. 10HashingA one-way function that turns data into a fixed-size fingerprint.
   11. 11Symmetric and asymmetric encryptionSymmetric encryption uses one shared key and is fast.
   12. 12Authorised testing and the lawIn most countries, accessing or testing a computer system without the owner's permission is a crime, whatever your intention.

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2. 2A safe home labThe setup for practising without hurting anyone: virtual machines, isolated networks, intentionally vulnerable apps, platform rules and notes.8 concepts

   1. 1Virtual machineA complete computer running as software inside your own, managed by a hypervisor such as VirtualBox, VMware Workstation or Hyper-V.
   2. 2SnapshotA saved state of a virtual machine that you can return to in seconds.
   3. 3Isolated lab networkA hypervisor network mode, such as host-only or internal, that lets lab machines talk to each other but not to your home network or the internet.
   4. 4Intentionally vulnerable appsApplications built with documented weaknesses so people can learn to find, fix and detect them legally, such as OWASP Juice Shop.
   5. 5Practice platform rulesEach platform's rules on what you may test (only the machines it gives you), what is banned (attacking the platform or other users) and what you may publish.
   6. 6Running targets in containersStarting practice apps and tools as containers, with ports published only on 127.0.0.1 so only your own machine can reach them.
   7. 7Lab notesOne page per exercise recording date, goal, steps, observations, meaning, and how the issue is prevented or detected, with captioned screenshots.
   8. 8Scripting for securitySmall scripts that read logs, filter and count events, or query a system, written in Python, Bash or PowerShell.

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3. How penetration testing worksWhat testers and bug bounty hunters do, the phases of an engagement and the authorisation that makes it legal. No techniques, just the profession.8 conceptsOpens with credits
4. Practising legallyWhere to build testing skill within the law: guided platforms, CTFs and bug bounty programmes, with their scope, safe harbour and disclosure rules.6 conceptsOpens with credits
5. Reporting and retestingThe part of testing the client actually pays for: a report people can act on, honest severity, useful fixes and a retest.7 conceptsOpens with credits
6. CertificationsWhat certifications prove, the common entry-level ones, the options for each path and the traps. Exam versions change: always check the official page.7 conceptsOpens with credits
7. PortfolioEvidence an employer can check: a few finished pieces for your path, write-ups you are allowed to publish, open source work and an honest profile.4 conceptsOpens with credits
8. Your first security jobRealistic entry routes, what junior roles expect, how technical rounds work and the scams that target beginners.7 conceptsOpens with credits
9. 9Glossary, A to ZEvery concept in the sheet and the smaller terms it uses, in one list.160 terms

Defend systems, test them, secure code.