How to Prevent Malicious Code

Summary

Malicious code is a crucial application security issue, and unchecked —  it can cause downtime, data exfiltration, financial loss, and more. This article on malicious code looks at the main kinds of malicious code to look out for, how to prevent malicious code, and how a comprehensive application security platform can be part of the solution. 

Malicious code, meaning any software or script that is intentionally designed to exploit vulnerabilities and cause harm is a growing challenge in application security. You can think of malicious code as the mechanism that an attacker uses to craft cyber attacks. Threat actors use malicious code to infiltrate devices and networks, take control of them, steal data from them, or otherwise cause damage. 

Top 5 Malicious Code Examples: Which of the Following is an Example of Malicious Code You Can Protect Against?

In application security, the most common kinds of malicious code include a variety of types of malware, each with its own specific characteristics and their own unique methods for compromising systems. Here are five of the most prevalent forms of malicious code.  

1. Viruses

A virus is characterized by malicious code that attaches itself to legitimate applications or files and then spreads by replication when those files are executed. There is usually a trigger that activates a virus, which could be an action by a user such as opening a file or launching an application. A virus payload can perform a wide range of harmful actions, including corrupting data, deleting files, stealing data such as credentials, or disrupting operations. Unlike many other forms of malicious code, a virus needs a host file or a program to spread. 

Examples of viruses are file infector viruses which spread when a specific program is run, macro viruses which use macros like MS Word and then spread when an infected document is opened, or boot sector viruses, which infect the boot sector of storage devices including hard drives or flash drives, and then activate when the system is rebooted. 

2. Worms

Unlike viruses, a worm can self-replicate and therefore spread autonomously across a business network without the need for a specific host file or any human interaction. This can lead to widespread disruption, and be more difficult to isolate and eliminate than other kinds of malicious code risks. By exploiting security vulnerabilities or weaknesses in network configuration or human error, they can operate independently, consuming bandwidth, congesting the network, and causing application and system disruption. 

A worm can even scan for further vulnerable systems to spread itself more widely, often carrying a payload that performs malicious actions such as deleting files, launching DDoS attacks, or delivering additional malware including ransomware.

3. Trojans

    

Trojans, or a Trojan horse is code that disguises itself as legitimate software or files and therefore can deceive a user into installing it intentionally. While trojans do not self-replicate, they can cause severe damage to application security. Once they have been installed, a trojan can install a backdoor or deploy Remote Administration Tools (RATs) to provide remote access to threat actors so they can manipulate applications or gain access to data. They can also disrupt operations by altering system settings, disabling security features, and stealing and corrupting data. 

Similar to worms, trojans also often carry additional payloads, such as ransomware or spyware, compounding their ability to damage the business. They may use evasion techniques to avoid detection such as disabling antivirus or using rootkit capabilities. They can also exploit vulnerabilities to gain elevated privileges, execute code, or spread across any given network. 

4. Ransomware

By encrypting data and locking users out of their systems, ransomware threat actors use malicious code in the hopes of receiving a ransom payment to restore access. It is increasing in prevalence, and ransomware was involved in almost a quarter of all breaches in 2023. Ransomware can be delivered through phishing emails, attachments, or by exploiting software and application vulnerabilities. It’s usually characterized by encryption, lockout, and a ransom demand. 

Ransomware makes data inaccessible and therefore disrupts business operations, and causes financial losses through the price of recovery, operational disruption, and reputational damage. If sensitive data is exposed or shared, it can also lead to heavy regulatory penalties. 

5. Spyware

Malicious code doesn’t always mean causing business disruption or attracting attention. Spyware is a type of malicious code that’s designed to monitor and collect information from a device while staying under the radar. It can collect personal information including credentials, browsing habits, financial information, and more, and then send this back to the attacker. It can maintain persistence through modifying system settings, installing rootkits, or working through fake scheduled tasks. 

Examples of spyware include keylogging software which records every keystroke, adware which can track user behavior and compromise privacy,  system monitors which capture application usage and internet activity, and infostealers —  designed to capture credentials, financial details, or documents.  

How Does Malicious Code Spread? 

The way that attackers spread malicious code will vary, depending on the kind of code they use. For example, they may use social engineering attacks which use malicious emails or websites that manipulate the user into disclosing sensitive information. Even within legitimate websites, scripts, or apps, attackers can also hide malicious code, and without comprehensive scanning, these can be missed. 

Threat actors might also uncover vulnerabilities in a network or a system which makes them particularly susceptible to malware or malicious code, and launch an attack from there, or they could take a step back and use a supply chain connection or another external party who a business works with in order to gain access to their main target. 

How Does Malicious Code Affect Systems?

If you’re wondering how you can identify malicious code once it’s already made its way into your system, you’re partly in luck. While some kinds of malicious code fly under the radar and remain invisible to security and development teams, in other cases there may be signs that your system has been infected. Here are some things to look out for: 

• Performance degradation: If your computers are significantly slower or less performant than they were, especially if the change has happened very quickly. 
• Unusual behaviors: Does your system or specific programs keep restarting or shutting down? This may be a sign of malware, especially if you’ve tried restarting manually.
• Spam: An increase in advertisements or unwanted pop-ups can often suggest that you may have inadvertently downloaded spyware onto your machine. 
• Hard drive capacity: If your teams suddenly notice an unexplained increase or decrease in the capacity of your hard drive, this could suggest that you have been a victim of malicious code.

How is Malicious Code Detected?

Malicious code is detected in a number of ways, depending on the kind of malicious code and where teams believe the malicious code to be a problem. One example is signature-based detection, where files are scanned for known patterns that have previously been seen in other malware samples. For unknown malware, heuristic analysis can often identify modified or new strains of malicious code by looking for suspicious patterns in code such as obfuscated code or abnormal system calls. Similarly, behavioral analysis can be used to flag suspicious actions such as unusual network activity or attempts that threat actors are making to modify system settings. The trick for these two approaches is to limit false positives.

One way to detect malicious code is to execute code in a sandbox environment so that behavior can be observed without risking any damage to the system. This allows for deeper inspection of the code, without opening the organization up to the threat of an attack. AI-based detection techniques are also becoming popular, where models are trained using machine learning algorithms on vast datasets so that they can accurately predict whether code is malicious. 

How to Avoid Malicious Code

To help with avoiding the impact of malicious code, here are a few general best practices to keep in mind which can reduce risk: 

• Implement code scanning and testing: Don’t assume that antivirus tools will catch all malicious code or malware attempts. Use additional scanning tools to check the security of your system as your teams move through the software development lifecycle. 
• Ensure you have robust security training for all: Security should be everyone’s responsibility, but not everyone has expertise. Look for team-specific training tools that allow everyone to learn what they need to incorporate security as part of their flow of work. 
• Block social engineering where possible: You’re only as strong as your weakest link. Adopt anti-phishing solutions, and speak to developers about their use of third-party OSS packages which may be manipulated by attackers on public registries. 
• Implement zero-trust/least privilege: The principle of least privilege means every user and application only has access to what it needs, and no further. This limits the damage potential if malicious code does make it past your first line of defense. 

Protecting Against Malicious Code Using Checkmarx One

A single holistic application security platform like Checkmarx One plays a vital role in supporting developers in preventing the risks associated with malicious code. Instead of adding friction between AppSec and Dev teams, integrated security tools such as SAST, SCA and AI security within the IDE means that developers can identify security flaws and vulnerabilities that may leave environments open to the risk of malicious code early in their cycle. Guided remediation and fixes take it further, allowing developers to then fix these vulnerabilities autonomously or at speed before they enter production environments or become prohibitively expensive to solve. 

We also have a dedicated solution for malicious package protection — helping developers to leverage public registries and third-party OSS packages without fear of manipulated or bad packages that may contain malicious code. 

Significantly reducing your exposure to the risks of malicious code needs to be top of your list of priorities. With the right tools, processes, and strategies —  organizations can stay two steps ahead, and build resilient and secure applications without slowing down the pace of innovation. 

Reduce the risk of malicious code in your DevSecOps environment with a single application security platform that covers the risk across your bases. Schedule a demo of Checkmarx One.