Security Coding Ques

## ✅ HIGH-FIDELITY PREP AREAS (IN PRIORITY ORDER)

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### 1. 🧠 **Log Parsing / Real-world Scripting**

> _“Write a script that parses logs and extracts X, or correlates logs A + B to find Y.”_

**Why it's high-fidelity**:
This tests your **Python fluency**, **real-world thinking**, and **security awareness**.

**Practice:**
- Parse Apache/Nginx logs and extract: IPs, timestamps, paths, status
- Correlate two logs using hashmap of lists
- Clean up dirty JSON or split a malformed CSV
- Defang/Refang IPs
- Detect anomalies or brute-force attempts

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### 2. 🧰 **LeetCode Easy/Medium (Security-Flavored)**

> _“Use dict/set/stack to solve this problem.”_

**Why**: Meta wants to know if you can **code competently**, not CS Olympics.

**High-fidelity set:**
- ✅ Group Anagrams
- ✅ Two Sum
- ✅ Valid Palindrome (with punctuation)
- ✅ Top K Frequent
- ✅ Simplify Path
- ✅ Valid IP Address
- ✅ Binary to Decimal
- ✅ Balance Parentheses
- ✅ Caesar Cipher
- ✅ Count frequencies, return top N
- ✅ Merge logs based on timestamp
- ✅ Add two numbers as strings

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### 3. 🔐 **Security Logic + Implementation**

> _“Write a Caesar cipher” or “Bruteforce a password file”_

**Why**: Shows **security awareness** in real-world scripting contexts.

**Practice:**
- Caesar/ROT13/substitution cipher
- Password bruteforce logic
- SSH botnet architecture (high-level design)
- Scan open ports on localhost
- Look for malware indicators in a binary string (Yara-like logic)
- Parse PDF metadata manually

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### 4. 🌐 **System Design with Security Focus**

> _“Design a scalable bot detection system”_

**Why**: Especially for IC5+ or system integration roles, this is key.

**What to know:**
- PKI / TLS / cert validation
- DLP vs EDR vs MDM tradeoffs
- Scaling log ingestion and alerting
- Designing secure API interactions
- OAuth / token validation / abuse patterns
- Secure file transfer, data retention, access control

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### 5. 🧪 **Regex, File IO, APIs**

> _“Extract all domains from a text file and hit an API for each”_

**Why**: Scripting + real-world glue.

**Practice:**
- Extract IPs, domains, emails using regex
- Read from file, write JSON result
- Call a REST API and parse response
- Clean malformed inputs (e.g., trailing whitespace, escaped chars)

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### Bonus: 🧱 **Build these for practice**

| Mini Project                      | What it reinforces                  |
|----------------------------------|-------------------------------------|
| Apache log parser                | File + string + dicts               |
| Top K frequent from a file       | dict + sort                         |
| Palindrome sanitizer             | stack + regex + punctuation logic   |
| PDF metadata scraper             | file parsing + data cleaning        |
| Bruteforce login simulation      | string gen + nested loops + control |

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## TL;DR – High-Fidelity Prep =

| Category              | Focus                                      |
|------------------------|--------------------------------------------|
| Python scripting       | Logs, files, strings, regex                |
| Easy/Medium LC         | dict/set/stack-based problems              |
| Real-world sec logic   | Cipher, metadata, bruteforce, signatures   |
| Security system design | TLS, auth, detection, log flow             |
| Practical tools        | Regex, APIs, file handling                 |

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Want me to create a **weekly schedule** where you rotate through each of these categories + mock exercises for each?









Cyphers / encryption algorithms

Implement a cypher which converts text to emoji or something.
Be able to implement basic cyphers.
Parse arbitrary logs

Collect logs (of any kind) and write a parser which pulls out specific details (domains, executable names, timestamps etc.)
Web scrapers

Write a script to scrape information from a website.
Port scanners

Write a port scanner or detect port scanning.
Botnets

How would you build ssh botnet?
Password bruteforcer

Generate credentials and store successful logins.
Scrape metadata from PDFs

Write a mini forensics tool to collect identifying information from PDF metadata.
Recover deleted items

Most software will keep deleted items for ~30 days for recovery. Find out where these are stored.
Write a script to pull these items from local databases.
Malware signatures

A program that looks for malware signatures in binaries and code samples.
Look at Yara rules for examples.


https://docs.google.com/spreadsheets/d/1IrTAb2-4zxcDc1t9snG2ls8nIo3PNiA4wh5VaqF8HGA/edit?gid=0#gid=0

Parse timestamp and IP from apache log files
—Correlate data from 2 separate logs, parse and store them using hashmap of lists so you can look it up in O(1) time later
—Count frequency of words that appear in a text
—Make API calls using requests and write tests for your methods
—Write a caesar cipher
—Leetcode easy string manipulation questions
—Leetcode medium string problems involving a stack






Amazon
jinchika
3d

1. Start practicing problems from here: https://neetcode.io/practice?tab=blind75
[Only the Easy and Mediums till Stack section should be sufficient mostly]
2. Then practice problems from here: https://leetcode.com/company/facebook/?favoriteSlug=facebook-six-months [Sort by frequently asked in last 6 months]. Again focus only on Easy and Medium from Arrays&Hashmaps, Sliding window, Two pointers and Stack categories.

Meta is known for asking the same facebook-tagged questions in leetcode.

I am not from Meta but interviewed there for security engineer position before. I followed above and was able to solve one medium in phone screen and two mediums in onsite coding round (all questions were from facebook-tagged leetcode ones)


Palindromes, two sum, IP validation, caeser cipher, that kind of stuff

1
Reply

Fastly
cYuN72
Yesterday

Nothing crazy. I was asked to write code to validate an ip address ipv4; validate a url


Domain specific question (security), leetcode easy (not meta tagged), behavioural and some sql. All reasonable, just not a lot of time, you have to move fast bc this is all in 45 minutes. Moved on to the final stage

I went through the process. I had questions around graph theory, traversal problem in coding round


It was for infra sec role. Other rounds were around building distributed security systems, analysis process and behavioral


Building scalable bot detection solution, how to detect ssl certs issued to domains similar to fb, malware detection process, sql queries on detecting badness from logs


Easy mediums, mostly focused on string manipulation combined with file handling, use of dicts/sets for indexing, etc.


Fb recruiters does a good job of providing everything you need to prepare for this role. Range of topics with less difficulty compared to other companies (even Amazon). If >=L5 System design only comes with prior experience I assume especially security focused design so ymmv


The question i got asked: code to output binary to decimal conversion

Also got asked: check if IP address is in the correct format

Data analysis is focusing on the different types of data you will encounter including logs, metadata, user data etc and how to use that data to understand the security environment.


Had to write code that would identify a palindrome, need to account for special characters. “Taco, cat” would be considered one, print the actual palindrome.


You can expect scripting questions like parsing the logs and building logic over it, defang IP, and enrichment of data set.


2 medium lc questions


Depends in which team, Prod sec vs Corp sec, etc. In general, know SSL / TLS, PKI, practical encryption, OWASP Top 10, strong Linux skills (including bash pipelines for text processing), strong scripting skills (e.g. Python), secure architecture. If a prod sec position add code auditing and some real SWE experience. If Corp sec add MDM, DLP, EDR, and infrastructure experience.



My screening was super easy..it was log parsing and splitting the string (I don't consider this LC). I have the onsite next. Any folks with experience if the technical is similar to the technical? The recruiter talked about the system design portion, but I am wondering if it is the typical SWE system design (design a URL shortener, messenger, etc). Any insights into this?



I got an interview call from Meta for Security Engineer - System integration role. What kind of questions can I expect?
1st round: Software security and threat modelling
2n round: Scripting, System Design, Software secuirty questions


71. Simplify Path variant


System design was design Leetcode (ironic eh) and security interview was a strange scenario based on PCI and iframes…


process is stupid, applying for appsec role should require coding related with bruteforcing, parsing api responses and stuff like that, not playing with effing arrays. We have docs and stackoverflow for that


Are you a sec eng rn? LC is like url parsing. Basically if youre good at SWE LC you only need to prep little for sec eng LC


I interviewed for meta for a security engineer and there was a coding portion. Had to write a script to identify palindromes but words with spaces and special characters need to be accounted for.



You’ll go through a series of interviews where they will test how good you are at writing code that works, for that, LeetCode 75 is the obvious thing to study.

Then, “find the bug” exercises. There will be multiple of them so be smart and be fast, speak clearly and don’t waste precious time saying dumb shit. If you don’t know, you don’t know.

Then, secure system design. They’ll present a short list of requirements to build a feature or system and you talk through the process with an emphasis on security.

Depending on the interviewer, you may also get some “hack this shit” type of question(s).



Looking at my notes I got LC easy-ish questions like balance parens, 3sum, and sum two binary numbers given as strings


Google security engineer has scripting questions mostly, on stuff like regex. Onsite may have 1 - 2 LC rounds.
Software security engineer is the same as software engineer with one security round onsite


Yes, there is a coding round, but it's more like a scripting round, leetcode easy. They just want to make sure you can code and hold your own in technical conversations with engineers.

Level is determined by your yoe and interview performance.

Ask your recruiter for the interview guide to help get an idea of what the interviews are like.


You will be asked to obtain root access to a python web server with 4 other candidates and a crowd of people screaming at you. Every 10 lines of code, you will need to take a shot. And every 15 minutes, you will need to take a shot.


Not FB but I had 2 scripting questions with Google for new grad security engineer. One was to parse some structured data from logs (so be familiar with python and JSON, dicts, files, etc). The other was to implement addition of two strings of integers - solution("1", "2")="3" . Both were pretty trivial and took under 15 mins; FB might have something similar to just know you can code.


Even people that code every single day I doubt can just do 30 questions and be able to pass. Blind 75 is already more than that. For me it took at least 100+ to start getting the pattern recognition and solving random questions down