From Ports to Payouts: Scanning Strategies for Bug Bounties

Bug bounty programs have become a cornerstone of cybersecurity, offering financial rewards to ethical hackers who find vulnerabilities in an organization’s systems. For aspiring and seasoned hackers alike, understanding and mastering scanning techniques can be pivotal to successful bug hunting. With numerous scanning tools and strategies available, it’s essential to have a well-rounded approach, particularly when it comes to effective port scanning, reconnaissance, and exploiting vulnerabilities.

In this comprehensive guide, we’ll take you through the different scanning strategies for bug bounties, explaining how to conduct port scanning effectively, leverage OSINT tools, utilize automated tools, and carry out vulnerability assessment for bigger payouts. By the end of this guide, you’ll have a solid foundation for approaching bug bounties with confidence.

Why Scanning is Critical in Bug Bounty Hunting

Before diving into the strategies, it’s essential to understand why scanning is a fundamental part of the bug bounty process. Scanning provides insights into a target’s open ports, services, and potential entry points for vulnerabilities. This initial phase is critical in laying the groundwork for identifying potential flaws, as it allows you to map the target’s attack surface thoroughly. Without proper scanning, you risk overlooking valuable vulnerabilities and missing out on potential payouts.

What Is Port Scanning?

Port scanning is a method for discovering the open ports on a networked computer, which reveals potential entry points for exploitation. Each port corresponds to a specific service or application that might be vulnerable, depending on how well it’s secured. By systematically probing these ports, you can identify which services are running, their versions, and any underlying vulnerabilities associated with them.

Common port scanning techniques include:

• TCP Connect Scanning: Establishing a full connection with the port.
• SYN Scanning: Often referred to as half-open scanning, this sends SYN packets to see if a response is received.
• UDP Scanning: Scans UDP ports, which are often overlooked but can expose critical vulnerabilities.
• ACK Scanning: Typically used to map out firewall rule sets.

Let’s delve into how you can use these port scanning methods as part of a broader bug bounty scanning strategy.

Step 1: Planning Your Reconnaissance

Reconnaissance, or “recon,” is the first step in identifying your target’s digital footprint. Effective reconnaissance goes beyond just port scanning and involves gathering as much information as possible about the target, such as domain names, IP addresses, subdomains, and exposed services. Some essential tools and techniques for reconnaissance include:

1. Subdomain Enumeration

Subdomain enumeration allows you to discover hidden subdomains within a target’s primary domain. Many times, sensitive information or outdated services are hosted on subdomains, making them ripe for vulnerabilities.

• Tools to Use: Amass, Sublist3r, Assetfinder, Knockpy, and crt.sh .
• Pro Tip: Combine multiple tools for exhaustive results. For example, run Sublist3r to get initial results, then use Amass to verify and uncover additional subdomains.

2. WHOIS Lookups and DNS Reconnaissance

WHOIS lookups provide registration details for a domain, potentially revealing information about the target’s network. DNS reconnaissance, on the other hand, focuses on understanding the structure of the DNS zones, which can provide insights into different subdomains or IPs related to the organization.

• Tools to Use: WHOIS, dig, nslookup, DNSDumpster, and Recon-ng.
• Pro Tip: If your target has several IP addresses, take note of them for further port scanning.

3. Passive Reconnaissance with OSINT

Open-Source Intelligence (OSINT) gathering helps you collect information about your target from publicly available sources. This non-intrusive technique is essential for learning about potential vulnerabilities without raising any alarms.

• Tools to Use: Shodan, Censys, and Google Dorking.
• Pro Tip: Shodan can be particularly useful for discovering open ports and exposed services, such as SSH or FTP, on the target’s IP address.

4. Use Automation for Recon

Reconnaissance can be time-consuming. Automate the repetitive parts by using tools like recon-ng, an all-in-one tool for OSINT, or a script like LazyRecon that combines subdomain enumeration, port scanning, and vulnerability detection.

• Pro Tip: Set up a VPS to handle automated scanning tasks. This way, you can run large-scale scans without slowing down your local network.

Step 2: Scanning Open Ports

Now that you have the target’s IP addresses and subdomains, it’s time to scan for open ports and discover running services. Here are some commonly used port scanning strategies:

1. Basic TCP and UDP Scans

Nmap is the go-to tool for port scanning and has various options for TCP and UDP scanning.

• Basic Command: nmap -sS -sU -p- -T4 target-ip
• -sS: SYN scan for TCP.
• -sU: UDP scan.
• -p-: Scans all ports.
• -T4: Speed of scan.
• Pro Tip: Start with a top 1000 port scan (using -F in Nmap) to get a quick idea of the open ports, then proceed with a full port scan.

2. Service Version Detection

Once you’ve identified open ports, it’s essential to detect the version of services running on them. By using Nmap’s version detection, you can find vulnerabilities tied to specific versions.

• Command: nmap -sV -p open_ports target-ip
• -sV: Enables version detection.
• Pro Tip: Run version detection along with scripts by using --script vuln to discover common vulnerabilities.

3. Advanced Scans with Masscan

Masscan is known for its high-speed scanning capabilities, allowing you to scan large networks in record time.

• Command: masscan -p0-65535 target-ip --rate 10000
• -p0–65535: Scans all ports.
• — rate: Controls the packet rate.
• Pro Tip: Use Masscan for initial scanning and combine with Nmap for more detailed scans.

4. Stealth Scanning Techniques

For bug bounty programs that have strict firewall protections, consider using stealth scanning techniques to avoid detection.

• Tools to Use: Nmap (SYN and ACK scanning), Scapy, and Hping.
• Pro Tip: SYN scanning (-sS) is often undetectable as it doesn’t complete the three-way handshake. Use ACK scanning to map out firewall rule sets and discover open ports hidden behind the firewall.

Step 3: Vulnerability Scanning and Analysis

Once you have a list of open ports and identified services, it’s time to analyze these services for potential vulnerabilities.

1. Using Nmap NSE Scripts

Nmap’s scripting engine (NSE) is incredibly powerful for vulnerability analysis.

• Command: nmap --script vuln -p open_ports target-ip
• Pro Tip: Run specific scripts like http-enum for web services, ftp-anon for FTP services, and ssl-heartbleed to check for the Heartbleed vulnerability.

2. Nikto for Web Servers

Nikto is a web server scanner that tests for outdated versions, insecure configurations, and known vulnerabilities.

• Command: nikto -h target-ip
• Pro Tip: Pair Nikto with other web application scanning tools, like Burp Suite, for a comprehensive analysis of the web service.

3. Using Vulnerability Databases

Use databases like the National Vulnerability Database (NVD), Exploit Database, or search for specific CVEs tied to the versions of services running on open ports.

• Pro Tip: Have tools like CVE Searcher installed to quickly reference vulnerabilities and their potential exploits.

4. Automated Vulnerability Scanners

Tools like OpenVAS, Nessus, and Qualys can perform detailed vulnerability scanning, mapping out potential exploits and known vulnerabilities.

• Pro Tip: Ensure to run vulnerability scans after hours or with the target’s permission, as they can be resource-intensive and potentially disruptive.

Step 4: Prioritizing and Exploiting Vulnerabilities

Now that you have identified potential vulnerabilities, it’s time to prioritize them and determine which ones offer the best chance of exploitation (and thus, the best payout).

1. Determine Exploitability

Not all vulnerabilities are exploitable. Conduct further research to see if there are existing exploits available for the vulnerabilities you’ve found.

• Tools to Use: Metasploit, searchsploit, and exploit-db.com .
• Pro Tip: Use Metasploit to automate exploit attempts, but ensure you’re following ethical guidelines, especially on live targets.

2. Chain Vulnerabilities

Sometimes, low-severity vulnerabilities can be chained together to create a higher-impact exploit. For instance, an open database port could be combined with default credentials to access sensitive data.

• Pro Tip: Look for default credentials, weak passwords, and configuration errors that can be chained with other vulnerabilities.

3. Document Your Findings

Bug bounty programs expect thorough reports that document your process, vulnerabilities found, and the impact of each. A detailed report not only improves your chances of getting a higher payout but also builds your credibility in the bug bounty community.

4. Responsible Disclosure

Ensure that you follow responsible disclosure policies set by the bug bounty program. Disclose only the vulnerabilities specified in the scope, and avoid sharing sensitive details publicly.

Conclusion

From ports to payouts, a successful bug bounty strategy hinges on effective scanning techniques, diligent reconnaissance, and prioritizing high-impact vulnerabilities. With the right tools and a methodical approach, you can uncover vulnerabilities that might otherwise go unnoticed, maximize your payouts, and contribute to a more secure digital world.

Bug bounty hunting requires patience, persistence, and continuous learning. As you gain experience, experiment with different tools, refine your scanning strategies, and share your findings with the bug bounty community. By doing so, you’ll not only improve your skills but also enhance your reputation as a valuable ethical hacker.

Good luck, and happy hunting!

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About the Author:

Vijay Gupta is a cybersecurity enthusiast with several years of experience in cyber security, cyber crime forensics investigation , and security awareness training in schools and colleges. With a passion for safeguarding digital environments and educating others about cybersecurity best practices, Vijay has dedicated his career to promoting cyber safety and resilience. Stay connected with Vijay Gupta on various social media platforms and professional networks to access valuable insights and stay updated on the latest cybersecurity trends.