What is Malicious Code? 3 Examples You Need to Know

By Tibor Moes / Updated: July 2023

What is Malicious Code? 3 Examples You Need to Know

What is Malicious Code?

When watching YouTube videos or reading emails, the last thing you worry about is security breaches. However, hackers can gain access to your system through malicious software if you’re not careful.

This malware allows people to steal your computer’s data and can wreak havoc on your mobile devices. It also exposes sensitive company data, which can cripple your business.

But what is a malicious code, and how does it hurt the victim’s system? This article will provide the answers.


  • Malicious code refers to any software or script intentionally created to harm, steal, or manipulate data in systems, encompassing viruses, worms, ransomware, and other harmful entities.
  • It infiltrates systems through various mechanisms, including email attachments, software downloads, and compromised websites, often relying on social engineering to trick users into activating the threat.
  • Robust defense against malicious code requires a multi-layered approach: using antivirus software, regularly updating all software, implementing strict access controls, and fostering user education on safe digital practices.

Don’t become a victim of cybercrime. Protect your devices with the best antivirus software and your privacy with the best VPN service.

What is Malicious Code?

Cyber attackers use malicious code to breach a computer and cause dangerous behavior. In most cases, it’s developed by tweaking existing computer programs, infrastructure, or files.

The threat has become widespread in recent years. Most breaches are performed through malicious code, since it can easily detect weaknesses in a PC. They create commands, scripts, or other phrases to exploit vulnerabilities, taking advantage of various entry points. Attackers can recreate and automate the malicious program through reusable components.

These automatic updates dramatically speed up data theft. If hackers could only use manual methods, it would take them too long to access Android devices, PCs, and other platforms.

But that’s not what happens. Instead, malicious code spreads and replicates through automation. Sometimes, the user doesn’t even have to interact or download the spyware to lose sensitive information.

To make matters worse, practically any component can be affected by malicious software. Smaller components (desktop and mobile apps) and large configurations (network infrastructure) are popular targets. Online servers and websites can also become infected.

That’s not all. Malicious programming can attack any gadget that operates on a computer, such as IoT devices. These include smart home platforms, modems, servers, routers, and in-vehicle infotainment systems.

Once cybercriminals find the ideal target, they breach the system with programs and scripts. From there, they can expose the attacked system to code, obtain private information, monitor its use, and gain deeper access.

There are various forms of malicious code, but they all have one thing in common – they follow distinct phases. Some of them operate autonomously, whereas others require special actions or human interactions to launch specific events. Most malware features the following structure.

·        Probing and investigating for vulnerabilities

·        Writing code to attack the system

·        Exposing the system to code

·        Executing the code using another program or built-in features

Efficiently controlled and executed, the code can initiate secondary malicious actions or replicate itself. Either way, the original malicious code moves from one gadget to another.

Well-executed attacks can use practically any channel to install spyware and trigger malicious traffic. The list includes many networks.

·        Online platforms (intranets, public websites)

·        Wireless connections (Bluetooth)

·        Social communications (pushed content, messaging apps, SMS, email)

Installing fishy plug-ins, clicking suspicious email links, opening attachments, and visiting infected websites are standard code gateways. The threat can enter your system through secret channels and explicitly malicious points.

Anything from a well-known software system to charging stations can transfer malware to your computer.

While the code package may not be obvious, you should be extra careful when using messaging services and public internet connections. Attackers regularly infect them with corrupt URL links or downloads to embed their software.

Types of Malicious Code

Malicious Code is a general term for system breaches. We’ve outlined the pattern of attacks, but this doesn’t mean every software infects your PC or phone the same way. There are several types of this code that behave differently from one another.


Viruses are forms of malicious code that self-replicate and attach themselves to numerous programs. The items travel through other files, enabling the malware to infiltrate the device. Once executed, it spreads through any connected network.

Trojan Horses

A Trojan Horse is a decoy file with malicious code that requires the user to activate the file and execute a particular program. Unlike computer viruses, Trojan Horses can’t spread autonomously or self-replicate. Still, their payload can harbor worms and other code.


Worms are similar to viruses because they self-spread and self-replicate. The only major difference is that they don’t require further action. Once they infiltrate a device, they execute actions by themselves without any programs.

Backdoor Attacks

Application backdoor code gives cybercriminals remote access to a compromised computer. Apart from jeopardizing sensitive data, it can also help the attacker become an advanced persistent threat (APT).

Consequently, they can easily explore the computer, wipe out data, and install spyware. Sometimes the attacks are so well-organized that they can endanger the networks of the U.S. government.

Cross-site Scripting

Cross-site scripting languages can interfere with your internet surfing by inserting malicious apps into your web applications. This can often change pushed content, infect your device, and intercept your information.


Ransomware encrypts a file after infecting it and holds it captive in return for a ransom. These breaches are generally preceded by Trojan Horses that set up a vulnerable gateway for the code.

This is a unique type due to its lucrative nature, which is why it’s become prevalent in moneymaking schemes. Operators that want to move from individual users to corporations utilize ransomware to reap higher payouts.

Examples of Malicious Code

Malicious code comes in several forms, but some are more famous than others. Here are the most popular instances of the attacks.

Emotet Trojan

Emotet Trojan first appeared in 2014, when it was developed as standard malware. Since then, it’s transported malicious code through email spam. The masterminds of this attack use urgent subject lines or other phishing tactics to persuade users to download infected files.

If it lands on your device, Emotet Trojan can run scripts with viruses or insert command and control server malware for severe infections. The attacks were temporarily halted in 2018, but they’ve returned as SMS malware.

Stuxnet Worm

The Stuxnet Worm has been invading computer infrastructures for more than a decade. The first breach took place in an Iranian nuclear facility through a flash drive and destroyed critical equipment.

In the meantime, the worm has been terminated, but the source code is still used to organize numerous breaches.

MegaCortex Ransomware

The most well-known instance of ransomware code is MegaCortex ransomware. To apply this tactic, the attackers paired up Qakbot and Emotet, two Trojans. This granted them quick entry to corporate networks.

The consequences were dire. Besides performing information theft and file encryption, cybercriminals also prevented all other users from accessing the network. There are two variants of this ransomware: MegaCortex Version 1 and MegaCortex Version 2.

Stay on the Safe Side

Nobody wants to lose data and money through malicious code. There are many ways to reduce the risk, like installing conventional antivirus software. Your browser’s pop-up blocker, firewall, and cautious surfing also help make your network impervious.

How to stay safe online:

  • Practice Strong Password Hygiene: Use a unique and complex password for each account. A password manager can help generate and store them. In addition, enable two-factor authentication (2FA) whenever available.
  • Invest in Your Safety: Buying the best antivirus for Windows 11 is key for your online security. A high-quality antivirus like Norton, McAfee, or Bitdefender will safeguard your PC from various online threats, including malware, ransomware, and spyware.
  • Be Wary of Phishing Attempts: Be cautious when receiving suspicious communications that ask for personal information. Legitimate businesses will never ask for sensitive details via email or text. Before clicking on any links, ensure the sender's authenticity.
  • Stay Informed. We cover a wide range of cybersecurity topics on our blog. And there are several credible sources offering threat reports and recommendations, such as NIST, CISA, FBI, ENISA, Symantec, Verizon, Cisco, Crowdstrike, and many more.

Happy surfing!

Frequently Asked Questions

Below are the most frequently asked questions.

What are ActiveX controls?

ActiveX controls are web add-ons that enhance your internet experience. They can also infect your PC and steal your data if misused.

What is anti-scripting software?

Anti-scripting languages can help prevent programs from performing unauthorized operations to lower the risk of malicious coding.

How do you deal with email viruses?

The best way to remove email viruses is to scan them with antivirus software. Also, avoid opening attachments that contain executable files.
Author: Tibor Moes

Author: Tibor Moes

Founder & Chief Editor at SoftwareLab

Tibor has tested 39 antivirus programs and 30 VPN services, and holds a Cybersecurity Graduate Certificate from Stanford University.

He uses Norton to protect his devices, CyberGhost for his privacy, and Dashlane for his passwords.

You can find him on LinkedIn or contact him here.