Security

Separate model quality from customer outcomes, then evaluate data, workflow, permissions, and switching costs in a hypothetical document service.

Explore IPv4 header fields, TTL, MTU-based fragmentation, and the risks and defenses associated with Ping of Death.

Compare the OSI and TCP/IP models, follow network encapsulation, and understand the security characteristics of hubs, switches, and routers.

Understand iptables’ four tables and five chains, and learn practical rules for default policies, blocking IPs, and allowing ports.

Learn how to audit and configure the core Linux server controls U-01, U-02, and U-03 from KISA’s vulnerability assessment guide for critical infrastructure.

Learn the roles of Windows event logs and how to investigate compromise using key event IDs such as 4624 and 4625, including detecting brute-force attacks.

Analyze Linux login records in wtmp, utmp, and btmp; trace abnormal access with last and lastb; and understand rsyslog.conf facilities and priorities.

Understand dictionary, brute-force, and rainbow table attacks, and learn how salting and key stretching defend against password cracking.

Distinguish viruses, worms, and Trojans, and learn how ransomware, APT attacks, and rootkits work.

Learn how race conditions and format string bugs exploit timing and unsafe C formatting, with attack scenarios and mitigations.

Learn process memory layout, how stack buffer overflows overwrite return addresses, and how ASLR, DEP, and stack canaries defend against these attacks.

Explore Windows authentication through LSA, SAM, and SRM, NTFS features, and how attackers abuse ADS to hide data.

Learn Linux process states, monitor them with ps and top, and schedule jobs securely with Cron and At.

Learn how SetUID, SetGID, and the Sticky Bit work, how privilege escalation abuses them, and how to audit special permissions with find.

Analyze Linux file permissions with ls -al, set octal permissions with chmod, and calculate default permissions with umask through hands-on examples.

Learn the Linux Filesystem Hierarchy Standard (FHS), analyze /etc/passwd and /etc/shadow field by field, and understand the security implications of UID 0.

Analyze the React2Shell vulnerability from a computer science perspective (serialization and RCE), and review general mitigations that are not tied to a specific cloud provider.

Learn how XSS, CSRF, and SQL Injection work, how they differ, and how to defend against them with output encoding, CSRF tokens, Prepared Statements, and other core techniques.

Understand the Same-Origin Policy, simple CORS requests, preflight requests, and how to resolve CORS errors correctly.

Learn the fundamental differences and behavior of cookies and sessions, their security and server scalability concerns, and the modern alternative JWT. Includes key interview questions and guidance for answering them.

Message authentication codes, HMAC construction and security, and block-cipher-based CBC-MAC.

Cryptographic hash requirements and the design of SHA-1, SHA-2, and SHA-3.

Explore elliptic curve cryptography, finite fields, point addition and doubling, scalar multiplication, ECDSA, and elliptic curve ElGamal.

An overview of schemes for verifying digital signatures, including RSA, ElGamal, and DSA.

Digital signature algorithms, correctness, message authentication, and security against chosen-message attacks.

An explanation of ElGamal encryption used in public-key cryptography.

The Diffie–Hellman key-exchange algorithm, examples, computational assumptions, and man-in-the-middle attacks.

An introduction to groups, subgroups, element order, cyclic groups, and the discrete logarithm problem.

Learn RSA key generation, encryption and decryption, correctness, CRT-based optimization, security limitations, and OAEP padding.

A guide to RSA, modular exponentiation, Euclidean algorithms, Euler’s phi function, Fermat’s theorem, the Chinese remainder theorem, and probabilistic primality tests.

An explanation of public-key encryption.

Stream ciphers, random and pseudorandom numbers, RC4, and an introduction to block-cipher modes.

An introduction to AES, its finite-field mathematics, encryption transformations, key expansion, and security.

Feistel structure, DES permutations, S-boxes, key scheduling, security, and Triple DES.

The structure and computational security of block ciphers.

An introduction to symmetric-key encryption, block ciphers, and stream ciphers.

Classical encryption techniques: shift, affine, substitution, Vigenère, permutation, and LFSR ciphers.

An introduction to the basic concepts of cryptography.

Computer security, the CIA triad, vulnerabilities, attacks, countermeasures, and security strategies.