OWASP M5: Insecure Communication Explained

Mobile applications are the backbone of both personal convenience and enterprise operations. With great connectivity comes great responsibility – when it comes to securing data in transit. OWASP Mobile Top 10’s M5: Insecure Communication highlights a critical and often exploited vulnerability where sensitive information is inadequately protected during transmission.

Whether it’s login credentials, API tokens, or personal user data, insecure communication channels leave mobile applications vulnerable to man-in-the-middle (MITM) attacks, packet sniffing, and data leakage. 

OWASP M5: Insecure Communication

OWASP M5: Insecure Communication refers to vulnerabilities that arise when data is transmitted over unprotected channels, making it susceptible to interception, modification, and exploitation by malicious actors. This can result in sensitive data leakage, session hijacking, and other security breaches. The core issue is the failure to properly encrypt or protect data as it moves between mobile devices, servers, and other endpoints, exposing it to attackers.

To view the full spectrum of mobile risks and how they interrelate, See A Guide to OWASP Top 10 Mobile Security Risks

Overview of OWASP Mobile Top 10 2023

The OWASP Mobile Top 10 is a globally recognized list identifying mobile applications’ most critical security risks. The 2023 edition, compiled through consensus among security experts, highlights the prevalence and severity of vulnerabilities in modern mobile apps. The list includes risks such as:

• Improper Platform Usage
• Insecure Data Storage
• Insecure Communication (M5)
• Insecure Authentication
• Insufficient Cryptography
• Security Misconfiguration

Importance of Secure Communication in Mobile and Web Applications

Secure communication is fundamental to protecting user privacy, safeguarding sensitive business data, and maintaining regulatory compliance. Implementing protocols like end-to-end encryption and Transport Layer Security (TLS) ensures that unauthorized parties cannot intercept or tamper with data transmitted between clients and servers. For users, secure communication fosters trust; it reduces the risk of costly data breaches and reputational damage for organizations.

Key benefits include:

• Protection against data interception and unauthorized access
• Compliance with industry regulations (e.g., GDPR, HIPAA)
• Enhanced user trust and brand reputation
• Prevention of financial loss due to cybercrime

Why Insecure Communication Is an Organizational Risk-Not Just a Developer Mistake

While insecure communication can result from developer oversights, its consequences extend beyond individual coding errors. When sensitive information is exposed due to insecure channels, the organisation faces significant risks, including financial penalties, legal liabilities, and loss of customer trust.

Cybercriminals increasingly target organisations through sophisticated attacks on mobile and web communication channels, exploiting any weaknesses to gain access to confidential data. Secure communication must be viewed as a strategic priority, requiring coordinated efforts across development, IT, compliance, and executive leadership.

The Growing Sophistication of Mobile Communication Attacks

Attackers continuously evolve tactics, leveraging advanced techniques such as man-in-the-middle attacks, session hijacking, and exploitation of outdated encryption protocols. The proliferation of mobile devices and remote work has expanded the attack surface, making it easier for adversaries to intercept unprotected data in transit. Modern attacks often bypass traditional security measures, targeting vulnerabilities in communication protocols and exploiting weak or misconfigured encryption.

This growing sophistication underscores the need for organizations to adopt up-to-date security standards, conduct regular audits, and educate developers and users about the importance of secure communication.

What is Insecure Communication?

Insecure communication is a critical vulnerability when data exchanged between a client (such as a mobile app or web browser) and a server is not adequately protected. This weakness exposes sensitive information, like login credentials, personal details, and financial data, to interception, manipulation, or theft by malicious actors. Insecure communication is a persistent threat in mobile and web application development and is a key focus area in security frameworks like the OWASP Mobile Top 10.

Mobile/Web App Development

In mobile and web app development, insecure communication refers to any instance where data is transmitted without proper encryption or security controls. This can happen during communication between the app and backend servers, third-party APIS, or devices over local networks. Developers often focus on building features and user experiences, but overlooking secure data transmission can leave applications vulnerable to attacks that compromise user privacy and organisational assets.

Insecure Communication in the Mobile Context

Insecure communication means that sensitive information sent or received by mobile applications is not adequately protected as it travels over Wi-Fi, cellular, or Bluetooth networks. Unlike web browsers, which often have built-in security features and visible indicators (like HTTPS locks), mobile apps must explicitly implement secure communication protocols. If these measures are absent or misconfigured, attackers can intercept network traffic, steal user data, or inject malicious content without the user’s knowledge.

Common Types of Insecure Communication

Insecure communication vulnerabilities occur when attackers can intercept, modify, or steal sensitive data transmitted between a mobile or web application and its backend server. These vulnerabilities arise from weak or improperly implemented security protocols, misconfigurations, or the absence of encryption altogether. Insecure communication can manifest in several ways, each presenting unique risks:

• Transmitting Sensitive Data Over Plaintext (HTTP): Sending data over HTTP instead of HTTPS means the information is unencrypted and visible to anyone monitoring the network. Attackers can easily capture usernames, passwords, credit card numbers, or other sensitive data as it traverses the network. 
• Weak/Improper TLS Usage: Transport Layer Security (TLS) is the standard protocol for encrypting data in transit. Using outdated versions (like SSL or early TLS), misconfiguring cipher suites, or accepting insecure renegotiation can undermine its effectiveness. Weak TLS usage leaves data vulnerable to decryption and manipulation by attackers.
• No Certificate Pinning or Validation: Certificate pinning ensures that an app only trusts specific, known certificates when establishing secure connections. Failing to validate certificates also opens the door to similar exploits.
• Hardcoded Endpoints with No Security Context: Some applications use hardcoded server addresses or API endpoints without enforcing secure connections or validating the authenticity of the destination. This practice can lead to data being sent to malicious servers if an attacker manipulates DNS or network routing, or if the endpoints themselves are compromised.

Typical Attack Vectors

Modern mobile and web applications face a range of sophisticated attack vectors that exploit insecure communication channels. Understanding these vectors is crucial for developers and organisations that protect sensitive data and maintain user trust.

Man-in-the-Middle (MitM) Attacks

Mitm attacks occur when a malicious actor secretly intercepts and potentially alters the communication between a user and an application or backend service. Attackers position themselves between the client and server by exploiting insecure Wi-Fi networks, ARP spoofing, or DNS poisoning. Once in place, they can read, modify, or inject malicious data into the traffic, frequently without either party knowing. Poor certificate validation or misconfigurations can leave apps vulnerable to MITM attacks even when encryption is used.

Eavesdropping, Packet Sniffing, and Replay Attacks

Attackers can use packet sniffing tools to capture unencrypted data as it traverses the network, especially over public or insecure Wi-Fi. Eavesdropping allows them to steal sensitive information like credentials, financial data, or personal messages. Replay attacks involve capturing legitimate data transmissions and retransmitting them to trick the system into granting unauthorised access or performing unintended actions. These attacks are particularly effective when communication is improperly encrypted or lacks mechanisms to detect duplicate or altered messages.

Mobile Emulator and Proxy Interception

Attackers often use mobile emulators and proxy tools (such as Burp Suite or Charles Proxy) to analyse and intercept app traffic. By routing app communication through a controlled proxy, they can inspect, modify, or replay requests and responses. Emulators also allow attackers to bypass device-level security controls, making it easier to manipulate app behaviour, uncover hidden endpoints, or test for vulnerabilities in how data is transmitted and received.

Abuse of Push Notification Systems

Push notification systems, especially those used for multi-factor authentication (MFA), are increasingly targeted by attackers. Techniques like push fatigue attacks or MFA prompt bombing involve repeatedly sending authentication requests to users until they approve one out of annoyance or confusion. If an attacker already has a valid username and password, this method can be highly effective in bypassing MFA protections and gaining unauthorised access to accounts or systems.

Reverse Engineering Apps to Discover Insecure Endpoints

Reverse engineering involves decompiling mobile apps to access their underlying code and resources. Attackers use this technique to discover hardcoded API endpoints, authentication mechanisms, or cryptographic keys. Once these endpoints are identified, attackers can craft targeted requests, exploit insecure communication channels, or bypass security controls. Reverse engineering also enables attackers to modify app behavior, inject malicious code, or repackage the app for distribution through unofficial channels.

Mobile-Specific Nuances

Mobile application security is shaped by unique challenges and nuances that set it apart from traditional web security. Unlike web applications, mobile apps operate in highly diverse environments, spanning different device models, operating systems, network conditions, and user behaviours, which introduces complexities for developers and security teams. Mobile apps often rely on third-party SDKS, open-source libraries, and backend APIS, each of which can introduce inherited vulnerabilities or supply-chain risks if not properly managed.

Third-Party SDKs Leaking Data

Third-party Software Development Kits (SDKS) are widely used to accelerate mobile app development, add features, and enable integrations. They can introduce substantial security and privacy risks if not properly vetted and managed:

• Data Leakage Risks: Many SDKS, especially those for analytics, advertising, or social media, collect and transmit user data, sometimes without the app developer’s full awareness. This can result in unintentional data leaks, regulatory violations (such as GDPR or CCPA), and loss of user trust.
• Supply Chain Attacks: A compromised SDK can be a vector for attackers to infiltrate every app. High-profile incidents like the XcodeGhost malware have demonstrated how a single vulnerable SDK can impact thousands of apps and users.
• Reverse Engineering and Tampering: Insecure SDKS are susceptible to reverse engineering, allowing attackers to extract sensitive logic, tamper with functionality, or clone proprietary algorithms. This not only exposes business logic but also enables fraud and abuse.

Background Sync & Push Notification Channels

Mobile apps frequently use background synchronisation and push notifications to deliver real-time updates and maintain seamless user experiences. These features can also introduce security and privacy risks:

• Background Sync Risks: APIS like the Background Sync API allow apps to defer tasks until a stable connection is available. While useful for offline functionality, they can be abused to exfiltrate sensitive data in the background, potentially without user awareness.
• Persistent Threats: Continuous background sync or periodic background tasks can turn a compromised app into a persistent infection vector, enabling long-term data exfiltration or participation in botnets and DDoS attacks.
• Push Notification Abuse: Attackers can exploit push notification channels to deliver malicious payloads, phish users, or trigger unauthorized actions. If not properly secured, these channels may leak sensitive metadata or be used for social engineering attacks.

Real-World Examples and Case Studies

Understanding the impact of insecure communication in mobile and web applications is best illustrated through real-world incidents and case studies. These examples demonstrate how vulnerabilities such as unencrypted data transmission and weak TLS configurations can be exploited by attackers, often leading to severe consequences for both users and organisations.

Case Study: Mobile Banking App Exposing Session Tokens via HTTP

A notable security assessment of mobile banking applications revealed that some apps transmitted session tokens and API keys over unencrypted HTTP connections. If a user accessed their banking app on an unsecured Wi-Fi network, an attacker could easily intercept these session tokens using packet sniffing tools. 

Once intercepted, the attacker could impersonate the user, gaining full access to their banking session and performing unauthorized transactions without detection. This type of session hijacking is hazardous as it bypasses even strong authentication mechanisms, allowing attackers to act with the same privileges as the legitimate user.

Example: Sensitive User Data Exposed Due to Lack of HTTPS

Multiple instances have occurred where mobile and web applications failed to enforce HTTPS, resulting in the transmission of sensitive information such as login credentials, personal details, or financial data in plaintext. Attackers monitoring network traffic, especially on public Wi-Fi, could eavesdrop and capture this data with minimal effort.

For example, session tokens sent over HTTP can be stolen and used to hijack user sessions, leading to unauthorised access to user accounts and confidential information.

How Threat Actors Exploit Weak TLS Setups

Even when applications use HTTPS, improper or outdated TLS configurations can introduce significant risks. Threat actors exploit weak TLS setups by targeting deprecated protocols, insecure cipher suites, or misconfigured certificates. For instance, if an app accepts self-signed or invalid certificates without proper validation, attackers can perform man-in-the-middle (MITM) attacks, intercepting and potentially altering data in transit. Failing to enforce strict certificate validation or using weak encryption allows attackers to decrypt sensitive information, impersonate servers, or inject malicious content into the communication stream.

Business-Level & Security Implications

Insecure communication in mobile and web applications exposes organisations to severe business and security risks. These risks extend beyond technical concerns and impact financial stability, regulatory compliance, brand reputation, and the core trust between a business and its customers.

Compromise of Sensitive User Data

When communication channels are not correctly secured, sensitive user data, such as personal identifiers, financial details, and health information, can be intercepted or leaked. This leads to direct economic losses from fraudulent transactions and chargebacks and puts users at risk of identity theft and other cybercrimes. The average data breach cost has reached $4.45 million globally, underscoring the escalating financial stakes.

Account Hijacking and Unauthorized Access

Attackers exploiting insecure communication can intercept session tokens, credentials, or authentication codes, leading to account hijacking and unauthorised access. This can result in fraudulent activities, data manipulation, and loss of control over user accounts or business systems. Such breaches often bypass robust authentication mechanisms, making them particularly dangerous for applications in banking, healthcare, and e-commerce sectors.

Legal and Compliance Risks (e.g., GDPR, PCI DSS, HIPAA)

Organisations are legally obligated to protect user data under GDPR, PCI DSS, and HIPAA regulations. Failure to secure communication channels can result in significant regulatory fines, legal claims, and mandatory breach notifications. For example, GDPR violations can lead to penalties of up to 4% of annual global turnover or €20 million, whichever is higher. Non-compliance can also trigger lawsuits from affected individuals, further increasing financial and reputational damage.

Brand Damage Through Leaked Customer Data

A data breach caused by insecure communication can severely erode user trust and damage a brand’s reputation. Consumers are increasingly privacy-conscious and expect businesses to handle their data responsibly. Publicised breaches often lead to negative reviews, loss of customer loyalty, difficulty acquiring new users, and a decline in user engagement. In some cases, the reputational fallout can have long-term consequences, including a drop in share price and competitive disadvantage.

Breach of Internal APIs via Reverse-Engineering

Reverse-engineering of mobile apps and APIS is a growing threat, enabling attackers to discover insecure endpoints, bypass security controls, and exploit business logic flaws. Once internal APIS are exposed, attackers can gain unauthorized access to backend systems, manipulate or steal sensitive data, and disrupt business operations. The risks are heightened by the availability of tools that simplify API reverse-engineering, making it easier for threat actors to identify and exploit vulnerabilities.

Attackers constantly threaten modern web and mobile applications by exploiting recurring patterns of vulnerabilities. These “common vulnerability patterns in the wild” are not just theoretical risks – they are observed regularly in real-world breaches and incidents, as highlighted by the OWASP Top Ten and industry reports.

These patterns often stem from mistakes in configuration, outdated security practices, or overlooked aspects of application design. Examples include missing encryption for data in transit, improper certificate validation, outdated TLS protocols, and insecure API endpoints.

Common Vulnerability Patterns in the Wild

Attackers constantly threaten modern web and mobile applications by exploiting recurring patterns of vulnerabilities. These “common vulnerability patterns in the wild” are not just theoretical risks – they are observed regularly in real-world breaches and incidents, as highlighted by the OWASP Top Ten and industry reports.

These patterns often stem from mistakes in configuration, outdated security practices, or overlooked aspects of application design. Examples include missing encryption for data in transit, improper certificate validation, outdated TLS protocols, and insecure API endpoints.

Missing Transport Layer Encryption

Failing to encrypt data in transit, such as transmitting sensitive information over HTTP instead of HTTPS, remains a widespread vulnerability. Without transport layer encryption, any data exchanged between client and server can be easily intercepted and read by attackers, especially on unsecured networks like public Wi-Fi. This exposes credentials, personal data, and other confidential information to eavesdropping and theft.

Improper or Absent Certificate Validation

Applications that incorrectly validate server certificates or accept self-signed or invalid certificates are highly susceptible to man-in-the-middle (MITM) attacks. Attackers can present fraudulent certificates to intercept and manipulate traffic, undermining encrypted connections. Proper certificate validation, including implementing custom trust policies or certificate pinning when needed, is essential to prevent such exploits.

No Encryption of Sensitive Payloads (Even Over HTTPS)

Some applications mistakenly assume that HTTPS alone is sufficient, neglecting to encrypt especially sensitive payloads (such as authentication tokens or financial data) within the application layer. This can be risky if HTTPS is terminated at a proxy or load balancer, or if internal network segments are less secure. Sensitive data should be encrypted before transmission, even when using HTTPS, to ensure confidentiality throughout the data’s journey.

Use of Outdated TLS Versions

Relying on obsolete protocols like SSL or early versions of TLS (e.g., TLS 1.0 or 1.1) exposes applications to well-known vulnerabilities and cryptographic attacks. Attackers can exploit weaknesses in these outdated protocols to decrypt or tamper with data in transit. Best practice is to enforce the latest TLS standards (such as TLS 1.3), turn off deprecated protocols, and regularly audit all certificates and cipher suites for compliance.

Client-Server Token Leakage

Attackers can intercept and misuse session tokens, access tokens, or API keys exposed in URLS, logs, or transmitted over insecure channels. Token leakage enables unauthorized access to user accounts or backend resources and is a common target in attacks against OAuth and API-driven applications. Secure token storage, short token lifespans, and transmission only over encrypted channels are critical defences.

Poor API Security in Edge Communication

APIS are frequent targets for attackers due to their direct access to backend systems and sensitive data. Common weaknesses include a lack of input validation, missing authentication, and insufficient rate limiting. Attackers exploit these flaws to bypass controls, exfiltrate data, or disrupt operations. Secure API design, including strong authentication, encrypted connections, and regular security testing, is fundamental to reducing risk.

Root Causes of M5 Vulnerabilities

The OWASP M5: Insecure Communication category highlights some of the most critical and prevalent mobile and web application security weaknesses. These vulnerabilities often stem from foundational issues in implementing encryption, certificate validation, and session management. Understanding these root causes is essential to building secure applications and protecting sensitive data from interception, manipulation, and theft.

Using Outdated or Weak Encryption Protocols (e.g., SSL)

A significant root cause of insecure communication is the continued use of outdated or weak encryption protocols such as SSLv2, SSLv3, and early versions of TLS (1.0 and 1.1). These protocols suffer from well-documented vulnerabilities, including POODLE and BEAST, which allow attackers to decrypt or manipulate supposedly secure communications. Servers that support weak cipher suites (like RC4 or 3des) or have misconfigured cryptographic settings are also at risk. 

Lack of Certificate Validation

Improper or absent certificate validation is another frequent cause of insecure communication. When applications do not correctly validate server certificates or accept self-signed, expired, or misconfigured certificates, they become vulnerable to MITM attacks. Attackers can present fraudulent certificates to intercept and manipulate traffic, even over encrypted channels. 

Certificate validation involves checking the certificate chain, expiration, allowed algorithms, and key usage, but implementation mistakes or oversights are common. Without robust validation, the security guarantees of TLS/SSL are easily undermined.

Poor Session Management and Token Leakage

Weak session management practices, such as insecure handling of session tokens or authentication credentials, can lead to session hijacking and unauthorized access. If session tokens are transmitted over unencrypted channels, stored insecurely, or not invalidated adequately after use, attackers can steal these tokens and impersonate legitimate users. Token leakage is hazardous because attackers can bypass authentication mechanisms and access sensitive accounts or resources directly.

Detection & Monitoring Challenges

Securing mobile applications in 2025 requires overcoming significant detection and monitoring hurdles, driven by the complexity of modern mobile ecosystems and evolving attack methodologies. Unlike traditional web environments, mobile apps operate across fragmented device types, network conditions, and third-party integrations, creating blind spots that attackers exploit.

As mobile threats evolve, organisations face significant obstacles in detecting and monitoring insecure communication and related vulnerabilities. The complexity of mobile ecosystems, reliance on third-party components, and limitations in visibility all contribute to persistent blind spots that attackers exploit.

TLS Downgrade Attacks Go Unnoticed

TLS downgrade attacks are particularly insidious because they exploit the handshake process between client and server, tricking both into using outdated and less secure protocol versions. Once the connection is downgraded, attackers can exploit known weaknesses in older TLS versions to intercept or modify sensitive data in transit. 

These attacks are difficult to detect in real time, as the handshake manipulation occurs at a low protocol level and often leaves few traces in standard logs or monitoring tools. Without specialised detection mechanisms, organisations may remain unaware that their supposedly secure communications have been compromised.

Obfuscated SDKs Hiding Leaky Behaviors

Mobile apps frequently integrate third-party SDKS for analytics, advertising, or feature enhancements. Some SDKS are intentionally obfuscated, making it challenging for security teams to inspect their behaviour or identify data leakage. This obfuscation can conceal malicious or negligent practices, such as unauthorized transmission of user data to external servers. As a result, sensitive information may be exfiltrated without detection, and traditional static or dynamic analysis tools may fail to flag these behaviours.

Mobile Apps Skipping Secure DNS or Failing to Pin

Many mobile apps fail to implement secure DNS (such as DNS over HTTPS) or enforce certificate pinning, leaving communications vulnerable to DNS spoofing and man-in-the-middle attacks. Without DNS security, attackers can redirect traffic to malicious endpoints.

The absence of certificate pinning further increases the risk, as apps may accept fraudulent certificates, making it easier for attackers to intercept or manipulate data. Detecting these weaknesses is challenging without deeply inspecting app configurations and runtime behaviours.

No Real-Time Inspection of Traffic from Mobile Clients

Unlike traditional web applications, mobile apps often communicate over encrypted channels, and their traffic may bypass enterprise monitoring solutions such as firewalls or intrusion detection systems. Without real-time inspection and analysis of mobile traffic, organisations have limited ability to detect suspicious activity, data exfiltration, or protocol downgrades as they happen. This lack of visibility allows sophisticated attacks to persist undetected, increasing the risk of data breaches.

Limited Visibility into App ↔ API ↔ Third-Party Flow

The data flow in mobile environments is complex, often involving direct communication between the app, backend APIS, and third-party services. Monitoring this entire chain is difficult, especially when third-party APIS or SDKS are involved. Many organizations lack comprehensive tools to track and correlate events across all components, resulting in blind spots where attacks or data leaks can occur unnoticed. This limited visibility hampers timely detection and response to security incidents, particularly those involving third-party integrations.

How to Identify M5 Vulnerabilities

Identifying M5 vulnerabilities, a critical category in the OWASP Mobile Top 10, is essential to safeguard mobile and web applications from data breaches and unauthorised access. These vulnerabilities primarily encompass insecure communication (e.g., unencrypted HTTP traffic, weak TLS protocols) and insufficient cryptography (e.g., deprecated algorithms, poor key management), exposing sensitive data to interception or decryption by attackers. Insecure communication flaws often stem from misconfigured SSL/TLS implementations, acceptance of invalid certificates, or cleartext transmissions of personally identifiable information (PII).

Tools and techniques for testing insecure communication

Testing for insecure communication is essential to protecting sensitive data from interception and tampering during transit. Security professionals use the following tools – OWASP ZAP, Burp Suite, and Mobsf – to identify and analyse these vulnerabilities.

OWASP ZAP

OWASP ZAP (Zed Attack Proxy) is a free, open-source penetration testing tool designed to detect web application vulnerabilities. It acts as a proxy between the tester and the application, enabling the interception, inspection, and modification of web traffic. Key features for testing insecure communication include:

• Active and Passive Scanning: ZAP can perform passive scans (monitoring traffic for insecure patterns) and active scans (sending crafted requests to probe for vulnerabilities).
• WebSocket Analysis: ZAP continuously monitors often overlooked Websocket traffic to detect potential eavesdropping or session hijacking risks.
• Automation and Integration: ZAP can be integrated into CI/CD pipelines for automated, ongoing security testing.

Burp Suite

Burp Suite is a comprehensive web security testing platform favoured by professional penetration testers. It offers automated and manual tools for in-depth application traffic analysis. For insecure communication testing, Burp Suite provides:

• Proxy Interception: Like ZAP, Burp Suite intercepts and displays HTTP/HTTPS traffic, enabling testers to identify unencrypted transmissions and improper certificate handling.
• Scanner and Intruder: Its automated scanner detects vulnerabilities such as weak SSL/TLS implementations, while the Intruder tool allows for customised attack payloads.
• Manual Testing Tools: Features like Repeater and Sequencer facilitate manual testing of specific requests and session management, which can reveal subtle flaws in communication security.

MobSF (Mobile Security Framework)

Mobsf is an all-in-one mobile application security testing framework that supports static and dynamic analysis. For insecure communication testing in mobile apps, Mobsf offers:

• Dynamic Analysis: Mobsf can run mobile apps in an instrumented environment, capturing and analysing network traffic to detect unencrypted data transmissions and insecure API calls.
• Integration with Proxies: It can be configured to work with tools like ZAP or Burp Suite, enabling interception and inspection of app traffic in real time.
• Static Analysis: Mobsf examines app binaries for hardcoded credentials, insecure configurations, and improper use of cryptographic APIS, which can contribute to insecure communication.

Security Scanning and Penetration Testing Best Practices

To effectively identify and address M5 vulnerabilities, follow these best practices:

• Asset Identification: Inventory all systems, applications, and network components to be assessed. This helps ensure comprehensive coverage and prioritisation.
• Automated Scanning: Use tools like OWASP ZAP, Burp Suite, and Mobsf to identify common insecure communication issues quickly. Automated scans should be complemented by manual testing for thoroughness.
• Manual Verification: Not all vulnerabilities can be detected automatically. To catch subtle issues, manually inspect traffic, especially for custom protocols or non-standard implementations.

Mitigation Strategies for Secure Communication

Securing communication channels is a foundational element of modern cybersecurity, as the risks of data interception, tampering, and unauthorised access continue to escalate in today’s digital landscape. Insecure communication, such as transmitting sensitive data without adequate encryption or using outdated protocols, can expose organisations to data breaches, financial losses, and reputational harm.

Mitigation strategies for secure communication focus on implementing strong encryption, enforcing strict certificate validation, and adopting layered defences to prevent man-in-the-middle (Mitm) attacks and data leakage. 

Always Use HTTPS/TLS with Strong Cipher Suites (TLS 1.3)

• Mandate HTTPS Everywhere: All data exchanges between clients and servers should occur over HTTPS, which leverages TLS to encrypt traffic and authenticate endpoints.
• Adopt TLS 1.3: TLS 1.3 is the most secure and efficient protocol version, offering faster handshakes, reduced latency, and mandatory perfect forward secrecy. It eliminates outdated ciphers and encrypts more of the handshake process, making downgrade and interception attacks far less likely.
• Use Strong Cipher Suites: Ensure only robust, AEAD (Authenticated Encryption with Associated Data) ciphers are enabled, and turn off weak or deprecated algorithms.

Enforce Certificate Pinning and Hostname Validation

• Certificate Pinning: Pin the server’s public key or certificate within your application to ensure it only trusts specific, known certificates if a rogue Certificate Authority (CA) issues a valid-looking certificate.
  • Public key pinning is preferred over certificate pinning for easier certificate renewal management.
  • Maintain backup pins to avoid service disruptions during certificate changes.
• Hostname Validation: Always verify that the server’s certificate matches the expected hostname or IP address. This prevents attackers from using fraudulent certificates to impersonate you.

Encrypt Sensitive Data in Transit – Even Over HTTPS (Defense-in-Depth)

• Double Encryption: For highly sensitive data, encrypt payloads at the application level before transmitting them over HTTPS. This adds another layer of protection in case the transport layer is compromised.
• Selective Encryption: This approach can be used for credentials, financial data, or personal identifiers, especially in high-risk environments.

Disallow Fallback to Plaintext Protocols

• Strict Transport Security: Implement HTTP Strict Transport Security (HSTS) to force browsers and clients to use HTTPS exclusively, blocking any fallback to insecure HTTP.
• Disable Legacy Protocols: Remove support for outdated protocols like SSL, TLS 1.0, and TLS 1.1, which are vulnerable to known attacks.

Avoid Transmitting Session Tokens via URL

• Use Secure Cookies or Headers: Never pass session tokens, authentication credentials, or sensitive identifiers in URLS, as they can be logged, cached, or leaked via referrers.
• Set Secure and HttpOnly Flags: Store tokens in cookies with the Secure and HttpOnly attributes to prevent client-side access and ensure they are only transmitted over HTTPS.

Enable Proper Mobile VPN Usage and Secure Transport Protocols

• Leverage Trusted VPNS: For mobile applications, reputable VPNS are required or recommended to protect data on untrusted networks, such as public Wi-Fi.
• Secure Transport Protocols: Use protocols like IPSec or Openvpn, which provide strong encryption and authentication for mobile data in transit.

Monitor for MitM Indicators and Anomalous Patterns

• Network Monitoring: Continuously monitor network traffic for signs of interception, such as unexpected certificate changes or abnormal handshake failures.
• Alerting and Response: Implement automated alerts for anomalies in traffic patterns, certificate validation failures, or protocol downgrades, enabling rapid response to potential threats.

Secure Usage of Third-Party SDKs

The secure usage of third-party SDKS is a critical concern for modern app development, as these components can greatly enhance functionality but also introduce significant security and privacy risks if not carefully managed. Third-party SDKS may contain vulnerabilities, mishandle sensitive data, or even serve as vectors for supply chain attacks, potentially exposing applications to data breaches, unauthorised access, or regulatory violations.

Audit SDK Data Flows

Understanding how data moves between your app and third-party SDKS is fundamental for security and privacy compliance.

• Map All SDK Integrations: Maintain an up-to-date inventory of all third-party SDKS in your application. Automated tools can scan your codebase to identify SDKS and map out data flows, showing what personal or sensitive data is shared and with which SDKS.
• Document Data Elements: For each SDK, document the transmitted data types (e.g., location, health, financial information) and ensure that only necessary data is shared.
• Continuous Monitoring: Implement ongoing audits to catch new SDK integrations or changes in data flows that might introduce new risks.

Require Security Documentation and Disclosures

Transparency from third-party SDK providers is crucial for evaluating and managing risk.

• Request Privacy Manifests: SDK vendors must provide privacy manifests or similar documentation that outlines their data collection and usage practices. For example, Apple mandates privacy manifests for SDKS, which are consolidated into a single report for easier review.
• Review Security Practices: Ask for detailed security documentation, including information on authentication methods, data encryption, and compliance with industry standards such as GDPR, HIPAA, or PCI DSS.
• Evaluate Provider Reputation: Before integration, research the SDK provider’s history, update frequency, and responsiveness to security issues.

Validate Third-Party Libraries and APIs for Secure Communication

Ensuring the security of third-party SDKS and their associated APIS helps protect your app and its users from data breaches and attacks.

• Secure Communication: Verify that all data exchanged with SDKS and their APIS uses strong encryption (e.g., TLS) both in transit and at rest.
• Authentication and Authorisation: Ensure SDKS implement robust authentication and authorisation mechanisms, such as short-lived tokens and strict role checks.
• Vulnerability Assessment: Conduct regular vulnerability assessments and penetration testing on third-party libraries and APIS to identify and remediate security weaknesses.

Developer Tips

Building secure mobile applications requires a proactive approach, especially regarding networking, dependency management, and API implementation. The following are actionable tips for developers to ensure their apps are resilient against evolving security threats on both ios and Android platforms.

Use Secure Network Libraries and Platform-Specific Best Practices (iOS, Android)

• Always Use HTTPS: Ensure all network communications use HTTPS, not HTTP, to encrypt data in transit. On iOS, enforce App Transport Security (ATS) to mandate secure connections; on Android, use HttpsURLConnection or libraries like Retrofit for secure requests.
• Implement Certificate Pinning: Add certificate pinning to protect against man-in-the-middle (MITM) attacks. This ensures your app only trusts specific server certificates, reducing the risk of connecting to malicious endpoints.
• Leverage Trusted Libraries: Use well-established libraries such as Retrofit (Android) or Alamofire (iOS) for networking. These libraries are maintained and widely adopted, supporting secure communication protocols that are out of the box.

Validate All Third-Party Dependencies

• Review and Audit Dependencies: Before integrating any third-party library or SDK, review its source, maintenance history, and community reputation. Regularly audit dependencies for vulnerabilities and outdated components.
• Update Frequently: Keep all libraries and SDKS up to date. Apply security patches promptly to minimise exposure to known vulnerabilities.
• Limit Permissions: Only grant the minimum necessary permissions to third-party libraries, following the principle of least privilege.

Ensure Secure Implementation of APIs

• Enforce Strong Authentication: Use secure authentication protocols such as OAuth 2.0 or OpenID Connect. Implement multi-factor authentication (MFA) where possible.
• Encrypt Data in Transit and at Rest: To prevent unauthorized access, always use SSL/TLS for data transmission and strong encryption (e.g., AES-256) for data storage.
• Validate and Sanitize Inputs: Rigorously validate and sanitize all data received through APIS to prevent injection attacks and data corruption.

Organizational Best Practices

Securing communication in mobile applications is not just a technical challenge- it requires a coordinated organisational effort spanning processes, people, and technology. Organisations should adopt the essential best practices to reduce the risk of insecure communication and strengthen their mobile app security posture.

Build Secure Communication Checks into SDLC and CI/CD Pipelines

• Integrate security controls and automated checks for secure communication (e.g., HTTPS enforcement, certificate validation) into your Software Development Life Cycle (SDLC) and CI/CD pipelines.
• Automate static and dynamic analysis tools to detect insecure communication patterns before code reaches production.
• Ensure every new build is scanned for vulnerabilities, and block deployments that fail security gates.

Conduct Dynamic Analysis in Staging and Production Environments

• Go beyond static code analysis by running dynamic security tests in staging and production.
• Simulate real-world attack scenarios, such as man-in-the-middle (MITM) attacks, to identify weaknesses in data transmission and reception.
• Monitor for insecure data transmission, deprecated protocols, or improper certificate handling during app operation.

Include Insecure Communication in Mobile Threat Modeling

• Explicitly address insecure communication risks in your threat modelling exercises, covering all data flows between the app, backend, and third-party services.
• Consider all communication channels (TCP/IP, WiFi, Bluetooth, NFC, SMS, etc.) and identify how sensitive data could be intercepted or manipulated.
• Update threat models regularly to reflect changes in app architecture or new integration points.

Educate Developers and Product Owners on Business Impact

• Conduct regular training sessions to help developers and product owners understand the real-world business consequences of insecure communication, such as data breaches, regulatory fines, and reputational damage.
• Share recent incident case studies and attack scenarios to make risks tangible and actionable.
• Foster a culture where security is a shared responsibility, not just a technical checkbox.

Enforce Secure API Usage Policies

• Mandate using secure communication protocols (TLS/SSL) for all API interactions.
• Prohibit outdated or deprecated cryptographic standards and require proper certificate validation.
• Regularly audit API endpoints for compliance with security policies and revoke access to non-compliant services.

Maintain Updated Security Testing Tools

• Continuously update and expand your suite of security testing tools to cover the latest threats and vulnerabilities.
• Use both open-source and commercial solutions for static analysis, dynamic analysis, and penetration testing.
• Schedule periodic reviews to ensure tools are practical and aligned with evolving security standards.

Regulatory Compliance & Industry Guidance

Maintaining regulatory standards and industry best practices is essential for mobile app developers, especially when handling sensitive data or operating in highly regulated sectors. Following is an overview of key requirements and guidance for PCI DSS, app store security, and NIST mobile security.

PCI DSS Mobile Transmission Rules

With PCI DSS 4.0 becoming mandatory from March 31, 2025, organizations handling payment card data must adhere to updated and more rigorous security requirements. For mobile applications, critical rules include:

• Encrypt Cardholder Data During Transmission: All cardholder data must be encrypted over open, closed, private, and public wireless channels. This protects against unauthorized interception and access during data transit.
• Client-Side Security: New requirements (6.4.3 and 11.6.1) mandate inventory and monitoring scripts running on client devices to prevent unauthorized modifications and third-party script abuse.
• Network Security: Maintain firewalls, monitor access points, and segment networks to isolate sensitive data environments.

Google Play & App Store Security Requirements

Both Google Play and Apple App Store enforce strict security and privacy standards for all apps distributed through their platforms:

• Google Play:
  • Privacy & Security by Design: Apps must use the latest Android security features and privacy controls, with 91% of installs now on Android 13 or newer.
  • Play Integrity API: Developers are encouraged to use this API to detect tampering, prevent fraud, and ensure apps run in secure environments.
  • Google Play Protect automatically: scans apps for malware, blocks harmful apps, and provides real-time code analysis. In 2024, it identified over 13 million malicious apps outside Google Play.
• App Store (Apple):
  • While not detailed in the search results, Apple similarly enforces requirements such as mandatory use of secure network connections (ATS), privacy disclosures, and regular security updates. Apps must also undergo rigorous review for compliance with privacy, security, and content guidelines.

NIST Mobile Security Guidelines

NIST provides foundational guidance for mobile security, widely referenced across industries:

• Data Protection: Encrypt sensitive data using strong cryptographic standards at rest and in transit.
• Authentication & Access Control: Enforce strong authentication, including multi-factor authentication, and restrict app permissions to the minimum necessary.
• Ongoing Monitoring: Continuously monitor devices and applications for signs of compromise or non-compliance.

Conclusion

As mobile applications continue to evolve and integrate deeper into users’ lives and enterprise ecosystems, the risks associated with insecure communication grow more severe. OWASP M5: Insecure Communication is not just a developer concern – it’s an organizational imperative. From outdated TLS protocols and improper certificate handling to unsecured third-party SDKs and reverse-engineered APIs, the threat landscape is vast and unforgiving.

Mitigating these risks requires more than just best practices – it demands continuous vigilance, proactive testing, and a culture of security-first development.

At SecureLayer7, we specialize in identifying and eliminating security blind spots through advanced penetration testing, mobile app security assessments, and secure code reviews. Our experts use tools like OWASP ZAP, Burp Suite, and MobSF to help you detect vulnerabilities before attackers do – ensuring your communication channels are resilient, encrypted, and compliant with industry standards.

Partner with SecureLayer7 to conduct a comprehensive mobile and API security assessment tailored to your product. Contact us today to secure your mobile ecosystem – before it becomes a target.

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