CompTIA Security+ Cheat Sheet
Ports, acronyms and concepts you must recognize instantly on the Security+ exam. Printable, exam-focused, no fluff.
Ports to know cold
| FTP | 21 (data 20) |
| SSH | 22 |
| Telnet | 23 |
| SMTP | 25 |
| DNS | 53 |
| HTTP / HTTPS | 80 / 443 |
| POP3 / IMAP | 110 / 143 |
| LDAP / LDAPS | 389 / 636 |
| SMB | 445 |
| RDP | 3389 |
| Syslog | 514 |
Core models
| CIA triad | Confidentiality · Integrity · Availability |
| AAA | Authentication · Authorization · Accounting |
| Symmetric encryption | One shared key (AES, DES, ChaCha20) — fast |
| Asymmetric encryption | Public/private key pair (RSA, ECC) — key exchange & signing |
| Hashing | One-way digest (SHA-256) — integrity, not encryption |
| Defense in depth | Layered, overlapping controls |
| Zero trust | Never trust, always verify |
Attacks & defenses
| Phishing | Deceptive messages → user training + email filtering |
| SYN flood | Half-open TCP connections → SYN cookies, rate limiting |
| SQL injection | Malformed queries → parameterized queries, WAF |
| XSS | Injected scripts → input validation, CSP |
| Man-in-the-middle | Intercepted traffic → TLS, certificate pinning |
| Ransomware | Encrypts data → offline backups, 3-2-1 rule |
| Least privilege | Minimum access necessary; review regularly |
| MFA | Something you know + have + are |