How to Pentest Mobile Apps?

A Short Guide to Pentesting Mobile Platforms Based On Experience

Penetration testing methodologies were honed in the era of hardened network perimeters. Mobile application pentesting must contend with platform fragmentation (iOS/Android/HarmonyOS/Hybrid), limited access, intricate UIs, diverse states, asynchronous behaviors and dynamic execution environments that make it more challenging than pentesting conventional apps. Mobile applications have irrevocably shattered those familiar boundaries, with apps continuously connected to multiple APIs amid a complex ecosystem, pentesting must evolve.

Evaluating mobile app security requires rethinking long-held assumptions. The testing scope should expand beyond infrastructure to the app itself, its underlying SDKs, and how it interacts with end-users, devices, networks and data. Adopt an external attacker's perspective to find weaknesses in this new expansive surface area.

Rather than following routines shaped for static networks, use mobile contexts to guide evaluation. Let threats and vulnerabilities unique to mobile apps determine methodology, not legacy pentest processes. The effectiveness of mobile pentesting depends on this paradigm shift in approach.Threats_Today

Mobile pentesting requires breaking free of preconceived frameworks. For example, simply extracting secrets like API keys from an app provides little insight. The critical question is - can those secrets enable backend resource access and data exfiltration? Testing must examine the breadth of impact across the entire ecosystem.

Additionally, compliance checkbox mentality leaves dangerous gaps. Meeting criteria like OWASP's API Top 10 is important, but insufficient. Adversaries are not confined to predictable vulnerability patterns. Every aspect of the mobile threat landscape must be scrutinized through the lens of an attacker.

Pentesting should explore creative multi-stage attacks chaining app vulnerabilities with network flaws, social engineering, and malicious tools. Testing must look beyond the app itself to its role in a broader ecosystem.

This mindset shift is key. Mobile pentesting succeeds when powered by an external adversary's perspective, not reliance on internal silos and frameworks. Evaluate not just discrete flaws, but holistic pathways to breach assets. Adopt hacker thinking to gain defender advantage.

Pentesting Mobile Apps and APIs Guidance by Phase

The table below provides some guidance for each pentesting stage. This guide will help you define your pentesting procedures and the tools required.

The first section covers the preparation phase and is extremely important. Don’t skim over or skip entirely this phase because it’s vital that both parties understand what the scope and goals of the testing are.

Testing Phase         Purpose Specific Guidance
Pre-engagement Planning To define the scope of testing. This is best done in collaboration with a pentesting company. Due to their vast experience, the pentesting company should be able to highlight all logistics and legal requirements for a successful pentest.
  • Use the company’s security policy to align your scope to pre-approved guidelines.
  • Specify the testing environment, app APIs, and versions for testing and what vulnerabilities will be explored.
  • Outline a communication plan that indicates the team, communication channels, and communication frequency.
Intelligence Gathering The purpose is for the pentester to collect information from the client organization to facilitate the pentesting process. The critical information required during this stage is:
  • Confirm if certificate pinning is applied to the APIs
  • Identify access to public APIs
  • Identify security countermeasures and determine if they’re effective
  • Determine the authentication method for API users
Threat Modeling To identify areas that need protection and identify remedy strategies for system security.  Threat modeling evaluates risk levels on exposed assets such as user credentials, level of exploitation on APIs, and countermeasures required for valuable assets. 

Next we move into the important technical work of searching for holes in the security arrangements and verifying if they can be exploited. As covered early, it is vital that exploitation be considered in its broadest sense, i.e. not constrained to testing specific vulnerabilities but rather considering exploitation through scripted impersonation of genuine mobile app traffic.

Testing Phase Purpose Specific Guidance
Vulnerability Analysis and Assessment This assessment aims at identifying security risks caused by vulnerabilities and flaws in an organization's systems.    
  • The scope of testing should dictate the extent of a vulnerability assessment.
  • If identifying mobile app loopholes is part of the scope, reverse engineer apps with a Mobile Security Framework (MobSF) to automate code assessments.
  • Apply OWASP Top 10 to test all vulnerabilities and effectiveness of countermeasures.
Exploitation  This phase establishes main entry points to an organization's systems and identifies high-value targets.    
  • This stage exploits entry point vulnerabilities to identify high target areas. Attackers primarily target authentication, authorization, and availability to breach security restrictions.
  • Pentesters can use custom API requests created with postman and Burp Suite pro to intercept app traffic, modify and replay it to APIs to identify potential attackers.

Lastly, we examine effective methods for pentesters to compile and present results in a way that provides clarity for security teams. This enables organizations to fully grasp mobile risks based on the findings, and take decisive actions to harden their defenses.

Testing Phase Purpose Specific Guidance
Final Analysis and Review
  • Document access methods to your organization’s systems, the value of compromised systems, and the value of information targeted.
  • At this stage, the pentester should clean up the environment, reconfigure access details used to penetrate the environment, and prevent unauthorized access into the system.
  • The final analysis identifies system strengths and vulnerabilities, likelihood, and extent of potential attacks.
  • The pentester should document each test scenario and the corresponding vulnerability and/or exploit.
  • Make recommendations on threat resolution and minimization strategies.
Apply Test Results
  • This stage involves reporting and reviewing recommendations made by the pentesting company.
  • The report should highlight insights and opportunities to improve mobile app/API security – i.e., entry points discovered, and remedy solutions.
  • Summarize final results from pentesting, security exposure, and measures to be applied to minimize potential threats.

Wrap Up

With mobile apps, security boundaries have evaporated. Adversaries can easily download apps, reverse engineer code, and analyze traffic patterns. This allows plentiful time to probe APIs, uncovering vulnerabilities or logic flaws. API risks are just the tip of the iceberg.

To adequately test mobile app security, pentesters must adopt a malicious mindset. Look beyond APIs to find creative attack paths like app store misuse, client code manipulation, and injection of rogue components. Mobile has created a loose perimeter. Think like an attacker to uncover weaknesses defenders have yet to imagine.

Only an expansive view into mobile's full threat landscape will produce actionable insights. Testing must look beyond APIs at how a bad actor views mobile clients, users, and infrastructure. This perspective shift is key to securing mobile in the brave new world of boundaryless computing.