fundamentals

The first ten minutes of any design review decide its quality. This answer shows the sketch, the one question that finds most bugs, and why controls come last.

Candidates who say 'everything is new' and candidates who say 'nothing is new' both lose this one. The answer that scores names exactly three differences and keeps the rest of the toolkit.

Reciting the six letters earns little. What scores is a diagram drawn aloud, one boundary walked in depth, and a list of threats with owners.

Definitions take ten seconds. The interviewer wants a worked failure: which layer broke, which one held, and why they did not break together.

Three words people use interchangeably, and a prioritisation question that exposes whether you have ever had a backlog of thirty findings.

Most candidates start by deleting the commit. The key was copied the minute it went public; the clock starts with revocation.

A penetration test is a controlled, authorised simulation of an attacker with a scope, rules and a report. The legal and planning parts are what separate it from an attack.

Most candidates say 'rings' and stop. The interviewer is listening for who enforces the boundary, where the kernel must distrust its caller, and why one kernel bug undoes every process boundary at once.

Isolation is enforced by page tables and credentials, then deliberately punched through by debuggers, shared memory and IPC. A strong answer names both the wall and the doors.

Reading rwx bits is the easy half. Interviewers check whether you know what execute means on a directory, why setuid binaries are an attack surface, and what the sticky bit does and does not protect.

The definition takes one sentence. The interview is about the four ways privilege actually moves, and why most escalations are misconfigurations rather than exploits.

Linux candidates often freeze here. The model is learnable in five nouns, and interviewers reward the one insight that matters: privileges in a token can matter more than group membership.

Interviewers listen for precision: an overflow is an out-of-bounds write, an over-read is a different bug, and a use-after-free is about lifetime, not bounds. Getting the taxonomy right is most of the easy question.

Tool names are not the answer. Interviewers want to know what each view can and cannot tell you, and why a decompiler's output is a hypothesis to be checked at runtime.

Typing a command sets off a chain: a system call, a permission check, a loader, dynamic linking and memory protections. Every step is a place security is enforced, and a place it can be bypassed.

A vulnerability is a gap between what the code assumes and what an attacker can make true. Nearly every one falls into a handful of root causes, and each has a matching way to find and prevent it.

The classic 'what happens when you type google.com' turned into a security question. Interviewers want the stack in order, with the attacker who sits at each layer and the control that removes them.

Encryption alone does not stop a man in the middle: you could be encrypting to the attacker. The property that matters is authentication, and every successful MITM is a story about how it was skipped.

A classic warm-up that rewards precision: what state the server keeps, why spoofed SYNs cost the attacker nothing, and how SYN cookies move that state into the sequence number.

NAT is not a firewall, and inbound rules are only half a policy. Interviewers check whether you know what each device decides, and why the outbound direction is where breaches are contained.

Attackers scan the whole internet continuously and know your forgotten test server before you do. The answer is an inventory built from several sources, compared with what is actually listening.

Interviewers do not want the seven OSI names recited. They want you to say which layer an attack lives at, because that decides which control can see it.

NAT drops unsolicited inbound packets as a side effect of bookkeeping, not policy. Port forwards, UPnP, outbound connections and IPv6 all walk around it.

A firewall is a list of match conditions evaluated in order against fields it can see, plus a table that remembers connections. Almost every firewall failure is in one of those three words: order, fields, remember.

The whole IPv4 internet is scanned many times a day. If a service answers, assume someone has already catalogued it.

The most common screen question in security. The answer that scores sorts all four by one property: whether there is a key, and who holds it.

The trap is answering 'which is better'. Every protocol you use daily runs both, each doing the job the other cannot.

TLS protects bytes on the wire between two endpoints. The scored answer lists what lies outside that boundary, so nobody mistakes 'we use HTTPS' for a security design.

Preimage, second preimage and collision resistance sound alike and protect different things. The birthday bound explains why the last one costs half the bits.

Most candidates can recite TLS 1.3. Interviewers ask for 1.2 because it is still everywhere, and because every change in 1.3 is the fix for an attack on 1.2.

A certificate is a signed statement with a short list of claims: this key, these names, these uses, this period, issued by this CA. Every validation failure you have seen is one of those claims not holding.

OpenSSL is two libraries and a command-line tool. Most TLS failures blamed on it are applications that never asked it to check the hostname, or told it to stop checking at all.

API keys identify a caller; OAuth delegates a user's authority. The scored answer picks by who is acting and on whose behalf, and makes API keys as safe as they can be when used.

Three bugs, one cause. The answer that scores names the cause, explains why parameters are structural, and lands on why prompts have no parameters.

Every attribute answers one question: over which connections, to which scripts, from which sites and to which hosts does this cookie travel? Get those four right and most session theft paths close.

Logging in is one moment; a session lasts hours or months. Most session bugs live in what happens between: identifiers that never change, timeouts nobody enforces, and logouts that only clear the browser.

The user clicks a button on your page while believing they are on someone else's. The fix is a response header that tells the browser who may frame you, not script that tries to escape the frame.

No error messages does not mean no injection. And the sort column is the one place where 'just use parameters' does not work, so you need a different fix.

Interviewers ask for the list to see whether you are current. They ask how you would use it to see whether you understand it is an awareness document, not a standard.

Most database breaches are not clever. They are a reachable database, an over-privileged account, a leaked credential or an exposed backup.

Both platforms sandbox apps and require signing; they differ in who decides what runs and how fast fixes arrive. Interviewers want the shared model first, then the differences that change a threat model.

Three words every SOC uses and many candidates blur. The answer that scores defines each by what it obliges you to do, and names the decision that turns an alert into an incident.

Malware is just software that does what its operator wants on your machine. Every stage leaves evidence, and every stage has a control that can stop it.

Three parts, each short. The answer that scores ends with a design rule about what may and may not live in a prompt.

A knowledge check with two traps: two editions are in circulation with different numbers, and reciting names earns little. Grouping the ten into entries and impacts, and applying them to a system, earns the rest.

Three definitions and one practical consequence. The consequence is the point: security tests split into deterministic checks and measured rates.

An easy question with a lot of surface area. The scored answer walks the pipeline left to right, names the attacker's lever at each stage, and ties each to one control.

Trace the proposal to its executor, resource policy and task scope. A valid credential or tool schema does not by itself authorize this particular action.

A schema can constrain fields and allowed values. Follow what remains: trusted facts, resource and task permissions, safe consumers and actual completion.

A motivation question that is really a skills question. The scored answer gives a specific reason, maps existing skills to AI security work honestly, and shows what you have already done to close the gaps.

Compare the control each interpreter enforces. Then review a fictional document-ranking feature without mistaking valid syntax, visible text or human review for permission.

Reason from learned behavior without inventing a hidden persona. Apply an explicit content policy, preserve legitimate fiction and test both missed violations and unnecessary refusals.

Follow individual fields from their authors through tools, summaries and actual model exposure. Separate service-authoritative identifiers from quoted prose, then check each output and operation.

One attacks the model's inputs, the other its upbringing. The phase decides the defence, and interviewers want you to say so.

Every model makes mistakes. An adversarial example is a mistake someone chose for it, and that changes how you measure and defend.

The guarantee is about what an observer can learn from your presence in the data, not about hiding the data. Epsilon bounds it; delta is the small print.

Compare actual scope and evidence across AI red teaming, penetration testing and benchmarks. The labels alone do not tell you which boundaries were assessed.

Seven characteristics that frame most AI governance conversations. The scored answer names them precisely and shows how security supports, and trades off against, the others.