What is malware?

Malware works by employing trickery to impede the normal use of a device. Once a cybercriminal has gained access to your device through one or more different techniques—such as a phishing email, infected file, system or software vulnerability, infected USB flash drive, or malicious website—they capitalize on the situation by launching additional attacks, obtaining account credentials, collecting personal information to sell, selling access to computing resources, or extorting payment from victims.

Anyone can become a victim of a malware attack. Although you may know how to spot some of the ways that attackers target victims with malware, cybercriminals are sophisticated and constantly evolve their methods to keep pace with technology and security improvements. Malware attacks also look and act differently depending on the type of malware. Someone who’s a victim of a rootkit attack, for example, might not even know it, because this type of malware is designed to lay low and remain unnoticed for as long as possible.

There are many types of malware out there—here are a few of the most common.


Adware

Adware installs itself on a device without the owner’s consent to display or download advertisements, often in popup form to make money off clicks. These ads often slow a device’s performance. More dangerous types of adware can also install additional software, change browser settings, and leave a device vulnerable for other malware attacks.


Botnets

Botnets are networks of infected devices controlled remotely by attackers. These networks are often used for large-scale attacks like distributed denial-of-service (DDoS) attacks, spamming, or stealing data.


Cryptojacking

With the rise in popularity of cryptocurrencies, mining coins has become a lucrative practice. Cryptojacking involves hijacking a device’s computing power to mine cryptocurrencies without the owner’s knowledge, significantly slowing down the infected system. Infections of this type of malware often begin with an email attachment that attempts to install malware or a website that uses vulnerabilities in web browsers or takes advantage of computer processing power to add malware to devices.

Using complex mathematical calculations, malicious cryptojackers maintain the blockchain ledger, or decentralized, digital recordkeeping system, to steal computing resources that allow them to create new coins. Coin mining takes significant computer processing power, however, to steal relatively small amounts of cryptocurrencies. For this reason, cybercriminals often work in teams to maximize and split profits.

Not all coin miners are criminals, though—individuals and organizations sometimes purchase hardware and electronic power for legitimate coin mining. The act becomes criminal when a cybercriminal infiltrates a corporate network against its knowledge to use its computing power for mining.


Exploits and exploit kits

Exploits take advantage of vulnerabilities in software to bypass a computer’s security safeguards and install malware. Malicious hackers scan for outdated systems that contain critical vulnerabilities, then exploit them by deploying malware. By including shellcode in an exploit, cybercriminals can download more malware that infects devices and infiltrates organizations.

Exploit kits are automated tools used by cybercriminals to find and exploit known software vulnerabilities, allowing them to launch attacks quickly and efficiently. Software that can be infected includes Adobe Flash Player, Adobe Reader, web browsers, Oracle Java, and Sun Java. Angler/Axpergle, Neutrino, and Nuclear are a few types of common exploit kits.

Exploits and exploit kits usually rely on malicious websites or email attachments to breach a network or device, but sometimes they also hide in ads on legitimate websites.


Fileless malware

This type of cyberattack broadly describes malware that doesn’t rely on files—like an infected email attachment—to breach a network. For example, they might arrive through malicious network packets, or small segments of a larger dataset transferred over a computer network, that exploit a vulnerability and then install malware that lives only in the kernel memory. Fileless threats are especially difficult to find and remove because most antivirus programs aren’t built to scan firmware.


Ransomware

Ransomware is a type of malware that threatens a victim by destroying or blocking access to critical data until a ransom is paid. Human-operated ransomware attacks target an organization through common system and security misconfigurations that infiltrate the organization, navigate its enterprise network, and adapt to the environment and any weaknesses. A common method of gaining access to an organization’s network to deliver ransomware is through credential theft, in which a cybercriminal could steal an actual employee’s credentials to pose as them and gain access to their accounts.

Attackers using human-operated ransomware target large organizations because they can pay a higher ransom than the average individual—often many millions of dollars. Because of the high stakes involved with a breach of this scale, many organizations choose to pay the ransom rather than have their sensitive data leaked or risk further attacks. However, payment doesn’t guarantee the prevention of either outcome.

As human-operated ransomware attacks grow, the criminals behind the attacks are becoming more organized. In fact, many ransomware operations now use a “ransomware as a service” model, meaning that a set of criminal developers create the ransomware itself and then hire other cybercriminal affiliates to hack an organization’s network and install the ransomware, splitting the profits between the two groups at an agreed-on rate.


Rootkits

When a cybercriminal uses a rootkit, they hide malware on a device for as long as possible, sometimes even years, so that it steals information and resources on an ongoing basis. By intercepting and changing standard operating system processes, a rootkit might alter the information that your device reports about itself. For example, a device infected with a rootkit might not show an accurate list of programs that are running. Rootkits might also give administrative or elevated device permissions to cybercriminals, so they gain complete control of a device and can do things like steal data, spy on the victim, and install additional malware.


Spyware

Spyware collects personal or sensitive information without the user's knowledge, often tracking browsing habits, login credentials, or financial details, which can be used for identity theft or sold to third parties.


Supply chain attacks

This type of malware targets software developers and providers by accessing source codes, building processes, or updating mechanisms in legitimate apps. Once a cybercriminal has found an unsecured network protocol, unprotected server infrastructure, or unsafe coding practice, they break in, change source codes, and hide malware in build and update processes. When the compromised software is sent on to customers, it infects the customers’ systems as well.


Tech support scams

An industry-wide issue, tech support scams use scare tactics to trick people into paying for unnecessary technical support services that might be advertised to fix a falsified problem on a device, a platform, or software. With this type of malware, a cybercriminal calls someone directly and pretends to be an employee of a software company or creates clickable advertisements designed to look like system warnings. Once they’ve gained someone’s trust, attackers often urge potential victims to install applications or give remote access to their devices.


Trojans

Trojans masquerade as legitimate software to trick people into downloading them. Once downloaded, they might:
 

• Download and install additional malware, such as viruses or worms.
• Use the infected device for click fraud by artificially inflating clicks on a button, ad, or link.
• Record the keystrokes and websites that you visit.
• Send information (for example, passwords, login details, and browsing history) about the infected device to a malicious hacker.
• Give a cybercriminal control over the infected device.
   

Worms

Mostly found in email attachments, text messages, file-sharing programs, social networking sites, network shares, and removable drives, a worm spreads through a network by exploiting security vulnerabilities and copying itself. Depending on the type of worm, it might steal sensitive information, change your security settings, or stop you from accessing files. Unlike viruses, worms don’t require any human interaction to spread—they replicate on their own.


Viruses

Viruses are one of the oldest forms of malware, designed to disrupt or destroy data on infected devices. They typically infect a system and replicate when a victim opens malicious files or email attachments.

Malware can cause significant harm to businesses, with consequences that extend beyond the initial attack and include:
 

• Financial losses. Financial costs, including ransoms, recovery expenses, and lost revenue during downtime, are a common result of malware attacks.
• Data breaches and privacy issues. Malware can lead to data theft, compromising sensitive information such as customer data or intellectual property.
• Operational disruptions. Attacks can bring business operations to a standstill when employees are prevented from accessing critical systems or data.
• Reputational damage. Public knowledge of an attack can erode trust and damage customer relationships and long-term business prospects.

Early detection of malware is critical to minimizing damage to your systems. Malware often shows subtle signs, such as slow performance, frequent crashes, and unexpected pop-ups or programs, which could signal a compromise.

Businesses use a variety of tools to detect malware, including antivirus software, firewalls, endpoint detection and response (EDR) systems, managed detection and response (MDR) services, extended detection and response (XDR) solutions, and cyber threat hunting processes. While EDR focuses on detecting and responding to threats at the endpoint level, XDR goes beyond endpoints to correlate signals across multiple domains, such as email, identities, and cloud apps, providing a comprehensive view of threats. MDR combines these tools with expert-led monitoring and response services, offering businesses additional support in managing threats.

When unusual activity is detected, running full system scans and reviewing logs can help confirm malware’s presence. EDR plays a critical role in this process by identifying and isolating compromised endpoints, while XDR expands detection across the organization, offering end-to-end visibility of attacks. MDR services further enhance this process with continuous monitoring and expert analysis, enabling faster, more effective responses. Together, these tools and services provide a unified approach to detecting and mitigating malware threats, helping businesses limit damage and maintain security.

Preventing malware requires a proactive approach to security, and removing it effectively depends on early detection and swift action. Organizations can block or detect malware attacks using a combination of antivirus programs and advanced solutions for threat detection and response, which provide a comprehensive way to identify and mitigate threats quickly.

Here are some ways to prevent a malware attack:


Install an antivirus program

The best form of protection is prevention. Organizations can block or detect many malware attacks with a trusted security solution that includes antimalware, such as Microsoft Defender for Endpoint. When you use a program like these, your device first scans any files or links that you attempt to open to help ensure they’re safe. If a file or website is malicious, the program will alert you and suggest that you not open it. These programs can also remove malware from a device that’s already infected.


Implement email and endpoint protections

Help prevent malware attacks with XDR solutions like Microsoft Defender for XDR. These unified security incident solutions provide a holistic, efficient way to protect against and respond to advanced cyberattacks. Building on the foundation of MDR, which combines expert-led monitoring with advanced detection tools, XDR takes security to the next level by integrating signals across endpoints, email, identities, and cloud applications. This expanded visibility enables organizations to identify and disrupt sophisticated attacks faster and with greater precision.

Also a part of Microsoft Defender XDR, Microsoft Defender for Endpoint uses endpoint behavioral sensors, cloud security analytics, and threat intelligence to help organizations prevent, detect, investigate, and respond to advanced threats.


Hold regular trainings

Keep employees informed about how to spot the signs of phishing and other cyberattacks with training sessions that are regularly updated to cover new developments in attacker tactics. This will teach them not only safer practices for work but also how to be safer when using their personal devices. Simulation and training tools help simulate real-world threats in your environment and assign training to end users based on the results.


Take advantage of cloud backups

When you move your data to a cloud-based service, you’ll be able to easily back up data for safer keeping. If your data is ever compromised by malware, these services help ensure that recovery is both immediate and comprehensive.


Adopt a Zero Trust model

A Zero Trust model evaluates all devices and users for risk before permitting them to access applications, files, databases, and other devices, decreasing the likelihood that a malicious identity or device could access resources and install malware. As an example, implementing multifactor authentication, one component of a Zero Trust model, has been shown to reduce the effectiveness of identity attacks by more than 99%. To evaluate your organization’s Zero Trust maturity stage, take our Zero Trust Maturity Assessment.


Join an information-sharing group

Information-sharing groups, usually organized by industry or geographic location, encourage similarly structured organizations to work together toward cybersecurity solutions. The groups also offer organizations additional benefits, such as incident response and digital forensics services, news about the latest threats, and monitoring of public IP ranges and domains.


Maintain offline backups

Because some malware will try to seek out and delete any online backups you have, it’s a good idea to keep an updated offline backup of sensitive data that you regularly test to make sure it’s restorable if you’re ever hit by a malware attack.


Keep software up to date

In addition to keeping any antivirus solutions updated (consider choosing automatic updates to simplify this), be sure to download and install any other system updates and software patches as soon as they’re available. This helps minimize any security vulnerabilities that a cybercriminal might exploit to gain access to your network or devices.


Create an incident response plan

An incident response plan will provide you with steps to take in different attack scenarios so that you can get back to running normally and safely as soon as possible.

Malware isn’t always easily detectable, especially in the case of fileless malware. It’s a good idea for organizations and individuals alike to keep an eye out for an increase in popup ads, web browser redirects, suspicious posts on social media accounts, and messages about compromised accounts or device security. Changes to a device’s performance, such as it running much more slowly, might also be a sign of malware infection.

For more sophisticated attacks against organizations that antivirus programs are unable to detect and block, Security Information and Event Management (SIEM) and Extended Detection and Response (XDR) tools provide security professionals with cloud-powered endpoint security methods that help detect and respond to attacks on endpoint devices. Because these types of attacks are multifaceted, with cybercriminals targeting more than just control of devices, SIEM and XDR help organizations see an attack’s bigger picture across all domains—including devices, emails, and applications.

Using SIEM and XDR tools, such as Microsoft Sentinel, Microsoft Defender XDR, and Microsoft Defender for Cloud, provides antivirus capabilities. Security professionals should ensure that device settings are always updated to match the latest recommendations to help prevent malware threats. One of the most important steps to take to prepare for a malware attack is to develop an incident response plan—a detailed, structured approach that organizations use to manage and mitigate the impact of cyberattacks, including malware infections. It outlines specific steps for identifying, containing, and eradicating threats, as well as recovering from the damage caused. Having a well-defined incident response plan helps businesses minimize downtime, reduce financial loss, and protect sensitive data by ensuring that all team members know their roles and responsibilities during a cyber crisis. This proactive preparation is key to maintaining business continuity.

If you’re worried that you’ve become a victim of a malware attack, fortunately, you have options for detection and removal. Immediate steps to take include:
 

• Running antivirus products, like the one offered natively in Windows, to scan for any malicious programs or code. If the program detects malware, it'll list the type and provide suggestions for removal. After removal, be sure to keep the software updated and running to prevent future attacks.
• Isolating affected systems. Keep malware from spreading by powering down the affected system or disabling the system’s network connectivity. Since malicious attackers might be monitoring organizational communications for evidence that their attack was detected, use atypical devices and methods—like phone calls or in-person meetings—to discuss next steps.
• Notifying stakeholders. Follow the notification guidance in your incident response plan to initiate containment, mitigation, and recovery procedures. You should also report the incident to the Cybersecurity and Infrastructure Security Agency, your local Federal Bureau of Investigations (FBI) field office, the FBI Internet Crime Complaint Center, or your local US Secret Service field office. Ensure compliance with data breach laws and industry regulations to avoid further liabilities.

As technology evolves, malware continues to adapt, becoming more sophisticated and harder to detect. Understanding future trends helps businesses stay ahead of threats.

Emerging types of malware are becoming increasingly sophisticated, often designed to bypass traditional security measures through obfuscation techniques. These techniques include polymorphic malware, which changes its code structure with each infection, making it harder to detect. Another example is malware that hides in legitimate processes or uses encryption to disguise its malicious payload. Fileless malware, which operates directly in memory without leaving a footprint, also evades detection by traditional antivirus programs. To combat these evolving threats, organizations need advanced solutions like AI-powered tools for cybersecurity that not only enhance detection and prevention efforts but also enable automatic attack disruption. These tools can isolate infected devices and suspend compromised accounts in real time, stopping threats in progress and limiting damage.

These tools improve detection rates by spotting anomalies or unusual behaviors that might indicate an attack, even before traditional methods would detect them. AI models can also predict potential threats by learning from previous attacks, enabling pre-emptive measures. Additionally, machine learning algorithms continuously refine detection capabilities, helping security teams stay ahead of evolving threats by predicting and preventing attacks before they happen.

To protect against malware threats now and in the future, organizations can rely on a AI-powered unified SecOps platform from Microsoft. This solution integrates advanced AI-assisted threat detection and automated responses to combat emerging types of malware. It brings together endpoint detection, threat intelligence, and cloud security, offering a unified platform for detecting, responding to, and preventing malware attacks in real time. By providing comprehensive visibility and automated protection across networks, this platform helps businesses strengthen their defenses against evolving threats.