What is malware?

Malware, short for malicious software, is one of the most pervasive and evolving threats in cybersecurity. It refers to any software intentionally designed to infiltrate, damage, or disrupt computer systems without the user’s knowledge or consent. Over the years, malware has grown from simple computer viruses into a sophisticated ecosystem powering everything from ransomware campaigns to espionage operations and large-scale botnets.

What makes malware so dangerous is its adaptability and reach. Cybercriminals continually refine their techniques to evade detection and target new platforms, including cloud environments, mobile devices, and even Internet of Things (IoT) infrastructure. Malware is the foundation for many of today’s most damaging attacks, serving as the entry point for ransomware, data theft, and network-wide disruptions.

The economics of malware also work in favor of attackers. Off-the-shelf malware kits and services on underground markets allow even inexperienced actors to launch campaigns at minimal cost. At the other end of the spectrum, advanced persistent threat groups develop highly customized malware capable of bypassing enterprise-grade defenses and remaining undetected for months.

As organizations adopt hybrid work models and expand their digital footprints, the risk surface for malware continues to grow. This article explores what malware is, the various forms it takes, how infections occur, and the serious consequences organizations face if they are unprepared.

This article will explore what malware is, its many types, how it works, and the devastating impacts it can have on organizations and individuals alike.

Malware explained

At its core, malware is any software created with the intent to cause harm. Unlike legitimate software that performs useful functions, malware executes unauthorized actions such as stealing data, encrypting files, or enabling remote control of systems.

The concept of malicious code dates back decades. The first computer virus, Brain, emerged in 1986, infecting floppy disks and displaying a copyright notice from its Pakistani creators. Since then, malware has grown exponentially in sophistication and impact.

Today’s malware is often modular, allowing attackers to tailor functionality for specific campaigns. Some strains include keylogging capabilities, data exfiltration tools, or ransomware payloads. Others are designed to evade detection entirely by running in memory or abusing legitimate system tools.

Modern malware campaigns are not isolated incidents. They are often part of larger operations orchestrated by criminal syndicates or state-sponsored groups seeking financial gain, competitive advantage, or political leverage.

Types of malware

Malware is not a single threat but an umbrella term for a wide range of malicious software designed to achieve different goals. Understanding these types helps organizations recognize the diverse tactics attackers use and tailor defenses accordingly.

Viruses
Viruses are one of the oldest forms of malware. They attach themselves to executable files and require user interaction, such as opening a file or running a program to activate. Once triggered, they can corrupt data, slow down systems, or spread to other devices. The ILOVEYOU virus, which appeared in 2000, infected millions of computers globally and caused an estimated 10 billion dollars in damages.

Worms
Worms take viruses a step further. They are self-replicating and can spread across networks without any user action. Worms exploit vulnerabilities in software or network protocols to infect systems rapidly. The WannaCry worm of 2017 is a prime example. It leveraged a Windows vulnerability to infect over 200,000 computers in more than 150 countries within days, disrupting hospitals, businesses, and governments.

Trojans
Named after the Trojan horse of Greek mythology, Trojans masquerade as legitimate software or files to deceive users into installing them. Once active, they can open backdoors for attackers, steal data, or deliver additional malware. The Zeus Trojan, infamous for targeting banking credentials, infected millions of computers and facilitated large-scale financial theft.

Ransomware
Ransomware encrypts a victim’s data and demands payment in exchange for a decryption key. Modern ransomware attacks often involve double extortion, where attackers also steal sensitive data and threaten to leak it publicly. Groups like LockBit and BlackCat (ALPHV) have refined this approach into highly profitable criminal enterprises.

Spyware
Spyware covertly monitors user activity, capturing keystrokes, screenshots, and sensitive information. It is often used for surveillance or to gather credentials for later attacks. Pegasus, a sophisticated spyware tool, has been deployed against journalists, activists, and political figures globally.

Adware
Adware delivers unwanted advertisements to users. While often considered less harmful, it can degrade system performance and, in some cases, serve as a conduit for more serious infections when combined with exploit kits.

Rootkits
Rootkits are designed to hide deep within a system, masking their presence from security tools and system administrators. They enable attackers to maintain long-term access and control over infected systems, making them particularly dangerous.

Fileless malware
Unlike traditional malware that writes files to disk, fileless malware operates in memory. It leverages legitimate system tools like PowerShell to execute malicious commands, making it harder for signature-based antivirus to detect. This stealthy approach is increasingly common in advanced attacks.

Botnets
Botnets are networks of compromised devices, often including IoT hardware like cameras and routers, that attackers control remotely. These networks can be used for spamming, launching distributed denial-of-service (DDoS) attacks, or spreading additional malware. The Mirai botnet demonstrated this in 2016 when it took down major websites like Twitter and Netflix with massive DDoS attacks.

How malware works

Malware infections rarely happen in a single step. Instead, attackers use a series of stages to infiltrate systems, establish control, and execute their objectives. Understanding this lifecycle is crucial for building defenses that can disrupt attacks at multiple points.

Delivery
The first step is delivery. Attackers use various methods to get malware onto a victim’s system. Phishing emails are the most common, containing malicious attachments or links that lead to infected websites. Drive-by downloads can also occur when a user visits a compromised or malicious website that silently installs malware. Other delivery methods include infected USB drives, malicious advertisements (malvertising), and software supply chain attacks where trusted software updates are compromised.

For example, the SolarWinds breach in 2020 demonstrated how attackers inserted malware into legitimate software updates, allowing them to infiltrate thousands of organizations globally.

Execution
Once delivered, the malware needs to run on the system. Some strains require user interaction, such as opening a file or enabling macros in a document. Others exploit vulnerabilities in operating systems or applications to execute automatically. Execution often involves dropping additional files, modifying system settings, or injecting malicious code into legitimate processes to evade detection.

Persistence
Sophisticated malware does not disappear when a device is restarted. It establishes persistence by modifying registry keys, installing services, or creating scheduled tasks that automatically execute the malware when the system boots. Some advanced strains even infect the firmware, ensuring survival through operating system reinstalls.

This persistence allows attackers to maintain access over time, which is especially dangerous for targeted attacks where they may lurk in networks for weeks or months before activating their payload.

Payload activation
At this stage, the malware begins performing its intended function. This can range from encrypting files in ransomware attacks to silently exfiltrating sensitive data in espionage campaigns. Some malware disables antivirus software or deletes system restore points to make recovery more difficult.

In the case of ransomware, the payload often displays a ransom note demanding payment in cryptocurrency within a limited timeframe to avoid permanent data loss or public exposure of stolen information.

Lateral movement and exfiltration
Many modern malware strains are designed to spread beyond the initially infected device. They scan networks for other vulnerable systems and use stolen credentials or known exploits to move laterally. Attackers often target backup systems and domain controllers to maximize their control and impact.

During this phase, sensitive data is often exfiltrated to remote servers under the attacker’s control. This data may include intellectual property, customer records, or financial information. Double extortion tactics have become common, where stolen data is used as leverage to pressure victims into paying.

Evasion techniques
To avoid detection, modern malware employs a variety of evasion techniques. These include encrypting its code, obfuscating commands, and using “Living off the Land” tactics where legitimate system tools such as PowerShell or Windows Management Instrumentation are abused for malicious purposes. Fileless malware, which operates entirely in memory, further complicates detection for traditional antivirus solutions that rely on scanning files.

Impacts of malware

Malware attacks are not just technical problems. They create cascading effects that can devastate organizations and individuals alike. From financial losses to reputational harm, the consequences often extend far beyond the initial infection.

Financial damage
One of the most immediate impacts of a malware attack is financial loss. Recovery costs often include forensic investigations, system restoration, legal fees, and in some cases, ransom payments. Downtime adds to the burden, with lost revenue and productivity compounding the damage. The 2017 NotPetya/WannaCry malware outbreak caused an estimated 10 billion dollars in global damages, crippling multinational corporations and critical services alike.

Data breaches
Many malware strains act as enablers for larger breaches, stealing sensitive data such as customer records, intellectual property, or login credentials. This stolen information is often sold on dark web marketplaces or used in secondary attacks, amplifying the initial damage. Organizations that suffer data breaches face long-term challenges with compliance and customer trust.

Operational disruption
Malware can bring entire organizations to a standstill. Hospitals have been forced to cancel surgeries and divert patients because ransomware locked electronic medical records. Manufacturing plants have shut down production lines after malware infiltrated industrial control systems. Even municipal governments have been paralyzed, unable to process taxes, issue permits, or deliver essential services.

Reputational harm
Trust is hard to win and easy to lose. Publicized malware incidents erode confidence among customers, partners, and investors. Studies show that organizations often experience a significant decline in customer retention following a breach. In the case of the 2023 MGM Resorts ransomware attack, widespread outages damaged the brand’s reputation worldwide.

National security risks
Some malware campaigns extend their reach to critical infrastructure and national security. The Stuxnet worm, discovered in 2010, demonstrated how malware could physically sabotage industrial systems. More recently, state-sponsored groups have used malware to target energy grids, government agencies, and supply chains, raising the stakes from corporate loss to geopolitical conflict.

Detection and prevention

Malware continues to evolve rapidly, but organizations can fight back with a multi-layered defense strategy. Combining advanced technologies, strong processes, and employee training is the best way to prevent infections and reduce their impact.

Advanced Endpoint Protection
Modern endpoint protection platforms provide more than just traditional antivirus. They use behavioral analytics and machine learning to identify suspicious activities, such as privilege escalation or unauthorized encryption. These systems can automatically isolate infected devices and prevent malware from spreading across networks. Rollback capabilities also allow restoration of files altered during an attack without relying solely on backups.

Threat intelligence
Staying ahead of threats requires real-time insights into the global malware landscape. Threat intelligence feeds give security teams up-to-date information on new malware variants, attack techniques, and indicators of compromise. By blocking known malicious domains and IP addresses, organizations can reduce their exposure to active campaigns.

Email and web security
Many malware infections begin with phishing emails or compromised websites. Email filters scan attachments and links for threats, while web filtering and DNS protection block users from accessing malicious sites. Together, these defenses disrupt attackers before their payloads can be delivered.

Immutable backups
Backups remain essential when prevention fails. To be effective, backups should be stored in an immutable format that prevents unauthorized modification. Regular testing of backup and recovery procedures ensures that systems can be restored quickly without paying ransoms.

Network segmentation and patch management
Network segmentation limits malware movement within environments by restricting access between systems. Routine patching of operating systems and applications closes vulnerabilities that malware often exploits, such as those targeted in the WannaCry and NotPetya outbreaks.

Security awareness training
Employees are often the first and last line of defense. Ongoing phishing simulations and training programs help staff recognize malicious emails and suspicious behaviors. This approach builds a security-aware culture that significantly reduces successful social engineering attacks.

AI’s role in malware evolution and defense

Artificial intelligence is changing the landscape for both attackers and defenders.

Offensive uses
Cybercriminals are beginning to use AI to make malware more adaptive and stealthy. Some malware now modifies its behavior in real time to avoid detection. Advanced strains can even analyze network environments to identify high-value targets before activating.

Defensive uses
On the defensive side, security teams use AI-powered analytics to scan vast datasets for anomalies. These systems detect subtle signs of compromise, such as irregular network traffic or changes in system behavior, and trigger automated responses to contain attacks.

Organizations that integrate AI into their security operations have reduced breach lifecycles by an average of 74 days and cut costs by over one million dollars, according to recent studies.

Responding to malware

Even with strong defenses, no organization is completely immune. A comprehensive incident response plan is critical for minimizing damage when an infection occurs.

Containment
When malware is detected, affected systems should be disconnected from the network immediately to prevent further spread.

Assessment
Security teams must determine the scope of the attack, identifying which systems are compromised and whether sensitive data has been stolen.

Eradication
Removing malware from infected systems requires careful cleaning to ensure no residual code or backdoors remain. In some cases, systems may need to be reimaged to guarantee a clean state.

Recovery
Once eradication is complete, systems can be restored from clean, tested backups. Compromised credentials should be reset, and multi-factor authentication enforced where possible to prevent reinfection.

Post-incident review
A thorough analysis helps identify how the malware gained entry and what can be improved. Organizations may also have to notify regulators or affected customers if data exposure occurred.

Conclusion

Malware has evolved into one of the most powerful tools in the hands of cybercriminals and nation-state actors. It enables data theft, operational disruption, and financial extortion on a global scale.

Organizations can reduce their risk by adopting a layered security strategy. This includes advanced endpoint protection, resilient and immutable backups, real-time threat intelligence, and employee training. Proactive preparation is critical because malware attacks are no longer a question of if but when.

Resilience is now the standard for cybersecurity maturity. Companies that invest in prevention and recovery will be best equipped to face the challenges of an ever-changing threat landscape.