External penetration testing is a security strategy that assesses an organization’s external-facing assets. These assets include web applications, virtual private network (VPN) solutions, routers, firewalls, and smartphones.

In an external penetration test, assessors attempt to breach an internal network by exploiting vulnerabilities on external-facing assets. Testers can also try to access confidential data using external-facing assets like emails, websites, and file shares.

The pen-testers first need to conduct reconnaissance on the organization’s assets. They must gather intelligence, including open ports, vulnerabilities, and general information about its password creation policies. Once they successfully breach the network’s perimeter, the external penetration test is done.

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Many processes comprise an external penetration test, which include:

  • Identifying firewall misconfigurations
  • Identifying and exploiting vulnerabilities
  • Locating and compromising administrative services and interfaces
  • Identifying other possible attack techniques

External penetration testing determines all potential attack vectors to compromise a system remotely. Experts recommend that organizations conduct external penetration tests annually or, at the very least, after any significant network change is made to an external-facing system or service.

Why Do Organizations Need External Penetration Testing?

External penetration testing could be likened to regularly checking if your front door locks and office alarms work. It ensures that no threat actors can get into your network through external-facing assets.

What Can Organizations Get Out of External Penetration Testing?

External penetration testing can give organizations detailed insights into their attack surfaces or all the possible entry points attackers can use to hack into their networks via their Internet-facing assets. It can help them:

  • Gain visibility on how remote attackers could compromise their public-facing systems
  • Get insights into how they can prioritize their security spending based on actual risks
  • Understand how attacks can occur to formulate incident response plans based on potential risks
  • Enhance the security capabilities of their information technology (IT) teams
  • Be confident that they are closer to achieving regulatory compliance

What Are the Steps in External Penetration Testing?

Effective external penetration testing requires performing various steps that include:

  • Reconnaissance: This involves information gathering before the pen-testers simulate attacks.
  • Vulnerability detection: This aims to discover flaws in systems, networks, and applications for pen-testers’ use.
  • Exploitation: This involves actively exploiting security weaknesses identified in the previous phase. Publicly available, in-house developed, or commercially available exploit kits can be used here.
  • Privilege escalation: After a successful compromise, the pen-testers will attempt to gain a stronger foothold within the organization. That involves gaining higher access privileges or breaching other systems to gain complete control of the network.
  • Data exfiltration: The pen-testers may extract data using various tools and techniques.
  • Reporting and delivery: The pen-testers document the issues identified according to their priority and give recommendations. All these are presented clearly and meaningfully to both technical and business audiences.

What Are the Usual External Penetration Testing Methodologies?

External penetration testing requires using various methodologies, such as:

  • Footprinting
  • Checking for public information and other potentially leaked data
  • System, port, and service vulnerability scanning
  • Manually testing for identified vulnerabilities
  • Intrusion detection and prevention system (IDS/IPS) testing
  • Password strength testing

What Tools Are Typically Used in External Penetration Testing?

External penetration testing tools can either be publicly or commercially available. These include:

  • Nessus: A proprietary vulnerability scanner developed by Tenable, Inc.
  • Metasploit: An open-source software that provides information about security vulnerabilities and aids in penetration testing and IDS signature development developed by Rapid7.
  • Burp Suite Pro: A commercially available set of tools for all-in-one web security testing.
  • Dirbuster/Dirb/GoBuster: An open-source brute-forcing tool for website directories and files and Domain Name System (DNS) records.
  • Nikto: An open-source command-line vulnerability scanner for web servers to find dangerous files or computer-generated imageries (CGIs), outdated server software, and other problems. It performs generic and server type-specific checks as well as captures and prints cookies received.
  • Sqlmap: An open-source pen-testing tool that automates structure query language (SQL) injection flaw and database server takeover detection and exploitation.
  • Recon-ng: An open-source intelligence gathering tool to reduce time spent harvesting information from publicly available sources.
  • Nmap: An open-source network scanner created by Gordon Lyon used to discover hosts and services on a network by sending packets and analyzing responses.
  • Hydra: A parallelized login cracker that supports several protocols.
  • Google Hacking Database (GHDB): An index of search queries to find publicly available information for the use of pen-testers and security researchers.
  • theHarvester: A pen-testing tool for gathering information like email addresses, subdomains, hosts, employee names, open ports, and banners from various public sources like search engines, Pretty Good Privacy (PGP) key servers, and Shodan.

Every external penetration testing exercise is unique because it should fit an organization’s environment. But the strategy is a must for companies that want to protect against all kinds of threats that can enter through external-facing assets.

Key Takeaways