Custom Software Security: 7 Threats and How to Prevent Them

Custom software security is more than a technical issue: it is an essential condition for the trust, performance and long-term viability of your digital tools. In a context where cyberattacks are increasing, it is crucial to identify potential threats from the earliest stages of development.

This article presents seven common risks, from phishing to code vulnerabilities and software dependencies. You will also find concrete, practical solutions to protect your applications and provide your users with a reliable and secure experience.

Password theft

Despite numerous awareness campaigns, the reuse of weak or already compromised passwords remains a common problem. As reported by La Presse recently, the most used passwords in Canada this year are once again “admin” and “123456.” When the same password is used across multiple platforms, it can become an entry point for an attacker, especially if that password appears in a data breach.

To protect your users, it is essential to enforce strong password management practices. For example, you can require a certain level of complexity when a password is created, or integrate an automatic check with services like Have I Been Pwned to detect passwords that have already been compromised.

Note, however, that these checks should only be performed when the password is temporarily available in plain text, such as at creation or login. Passwords must never be stored in plain text in the database. Instead, use a proven hashing algorithm like bcrypt or Argon2.

Finally, add an extra layer of security by enabling two-factor authentication (2FA). Prefer app-based methods (TOTP) or email-based options, since text messages (SMS) are more vulnerable to interception attacks.

Code vulnerabilities

Some of the most destructive web attacks stem from vulnerabilities introduced directly into an application’s code. Flaws such as SQL injection or XSS (Cross-Site Scripting) can allow an attacker to run malicious code, view sensitive data, or completely disrupt the user experience.

To reduce these risks, a first step is to implement static code analysis tools. These tools can automatically detect certain security flaws before the application is even put into production.

Another good practice is to properly configure security-related HTTP headers. Directives such as Content-Security-Policy or X-Content-Type-Options help prevent unsafe browser behavior. Tools like Security Headers let you check at a glance whether your application complies with these standards.

It is also crucial to perform rigorous code reviews and to raise your development team’s awareness of application security best practices. Collaboration between developers, security experts and testers is essential to deliver robust, reliable and secure software.

Distributed denial-of-service (DDoS) attacks

A DDoS attack aims to overwhelm an online service by generating abnormally high traffic. The result? Your application becomes slow, unstable or completely unavailable. This type of attack is increasingly common, especially for publicly accessible services.

One of the first measures to protect against this is to use a content delivery network (CDN) combined with a web application firewall (WAF). This duo filters malicious traffic before it reaches your infrastructure. At Exolnet, for example, we can help you build an AWS architecture resilient to this type of attack.

Even outside of attacks, traffic from bots (crawlers) can unnecessarily load your system. Some bots are harmless, but others can be used to scrape your data or to train AI models without your consent. To limit their impact, configure your site’s robots.txt file correctly—this tells well-behaved bots which pages may or may not be crawled.

Another good practice is to optimize your error pages, such as 404s, so they are handled quickly by the server. This reduces load during an attack or an automated scan.

Preparing for DDoS attacks means ensuring continuity of service, even in critical moments.

Malicious software (malware)

Malware is designed to disrupt, damage or gain unauthorized access to a system. In software development, one of the most common entry vectors for malware is file uploads. A flaw in this feature can allow an attacker to install malicious software on your server.

To protect against this, start by implementing strict validation rules for uploaded files. This includes checking the MIME type, file size and allowed extensions. It is also advisable to automatically scan all files with an antivirus such as ClamAV. Make sure virus definitions are kept up to date to stay protected against the latest threats.

Beyond files, a good server monitoring system is essential. Unusual behaviours, such as abnormal CPU usage or suspicious login attempts, can reveal an infection. For example, a malicious cryptocurrency miner could run in the background and slow your operations without immediate notice.

Vigilance, combined with automated detection tools, makes it possible to react quickly before malware causes significant damage.

Phishing

Phishing is a well-known but still highly effective fraud technique. It involves tricking users by posing as a trusted entity (such as a bank, a service provider, or even your company) in order to extract sensitive information, such as passwords, card numbers or verification codes.

Even if attacks do not target your application directly, they can compromise your overall security if a user divulges their access credentials. That is why it is important to protect your company’s digital identity to prevent someone from impersonating you.

To do this, ensure your email domain is properly protected with authentication protocols. These let mail servers verify that emails sent in your domain’s name actually come from your authorized servers. The main mechanisms to implement are:

• SPF (Sender Policy Framework) to define which servers are allowed to send email on your behalf.

• DKIM (DomainKeys Identified Mail) to digitally sign your emails and confirm they have not been altered.

• DMARC (Domain-based Message Authentication, Reporting and Conformance) to control the enforcement of your authentication policies and receive reports on impersonation attempts.

By correctly configuring these three protocols, you significantly strengthen your domain’s security and reduce the risk of fraudulent or malicious emails sent in your name.

At the same time, raise awareness among your users and employees about the signs of phishing. A suspicious link, an unexpected attachment or an urgent request for personal information are all red flags to take seriously.

Preventing phishing protects not only your users but also your organization’s reputation.

Man-in-the-Middle attacks

A Man-in-the-Middle attack occurs when an attacker intercepts communication between two parties without their knowledge. The goal is often to capture sensitive data like passwords, card numbers or session tokens. In the worst cases, the attacker can even modify exchanges or impersonate one of the participants.

To prevent this type of attack, it is imperative to enforce HTTPS encryption across all your pages, without exception. Enabling HSTS (HTTP Strict Transport Security) strengthens this protection by forcing browsers to use a secure connection, even on first visit.

Session tokens should also be configured to be sent only over secure connections (Secure) and inaccessible to JavaScript (HttpOnly). These measures prevent their interception or manipulation.

Add security headers like Content-Security-Policy, X-Frame-Options, X-XSS-Protection, X-Content-Type-Options and Referrer-Policy to limit client-side attack vectors.

Finally, strengthen user session security by enabling two-factor authentication (2FA) and monitoring unusual IP addresses or suspicious multiple logins.

These complementary layers of defence help secure end-to-end exchanges and preserve the integrity of your communications.

The often-forgotten area in custom software security: the dependency chain

Software development relies heavily on open source libraries and components. While they speed up development, these tools also carry a risk: if one of them is compromised, it can serve as an entry point for an attack on your application. This is known as a supply chain or dependency chain attack.

In recent years this type of attack has become increasingly talked about because it targets the ecosystem rather than the core code. Organizations focus on securing their own application but often forget that each dependency adds another potentially vulnerable link. The dependency chain thus becomes the blind spot in custom software security.

To reduce this risk, start by locking your dependency versions using lock files such as package-lock.json or composer.lock. This prevents inadvertent inclusion of new, potentially vulnerable versions.

Make sure to maintain the applications you develop and integrate automated analysis tools such as Dependabot, Snyk or npm audit. These solutions monitor your dependencies and alert you as soon as a vulnerability is detected. Some can even suggest or apply automatic fixes, reducing reaction time.

Finally, before adding a new library to your project, take the time to verify its reliability. Check the update history, maintenance frequency and the reputation of its authors. A popular, well-maintained dependency generally presents fewer risks than an obscure, poorly documented module.

Your application’s security depends not only on your own code but also on the code you choose to adopt. A rigorous approach to dependency management directly contributes to your software’s resilience.

In summary: cybersecurity is a collective responsibility

Custom software security is not optional; it is a shared responsibility at every stage of development. Take the time to evaluate the security of proposed solutions to avoid introducing risks as early as your request for proposals.

Throughout this article, you learned about seven common threats custom software can face: password theft, code vulnerabilities, DDoS attacks, malware, phishing, Man-in-the-Middle attacks and vulnerabilities in the dependency chain.

For each threat, preventive measures exist and are within reach of all teams. With a collective effort and a rigorous, proactive approach, you can deliver high-performing, secure digital solutions worthy of your users’ trust.

Does your application have security concerns? Talk to our experts to identify modernization solutions tailored to your reality.

FAQ

What is a threat to custom software security?

A software security threat is any internal or external risk likely to compromise the confidentiality, integrity or availability of an IT system.

What types of threats can affect software?

Software can be threatened by password theft, code vulnerabilities, DDoS attacks, malware, phishing, Man-in-the-Middle interceptions and flaws in the dependency chain.

What protection measures are possible for software?

Protecting software relies on a multilayered approach combining secure coding, encryption, dependency checks, 2FA, secure HTTP headers, continuous monitoring and strict access management.

How can a vulnerability in custom software be detected?

A vulnerability can be detected through automated scans, code reviews, security audits, penetration tests, real-time monitoring and dependency assessments, which together allow you to identify and fix flaws quickly.