What Is Spyware? Types, Risks, and Prevention Tips

There are many types of malware that sneak into devices and either extract information or spy on the users, but none is as common as spyware. For instance, statistics reveal that 80% of internet users have been affected by spyware in one way or the other. It is thus important to understand what spyware is, which includes how it infiltrates a system and how one can prevent it from penetrating an organization’s computer systems. This comprehensive article covers all the aspects, including the history of spyware, its types, actual cases of spyware infiltration, and practical tips on how to protect yourself against spyware.

We will begin by explaining spyware meaning and the ways criminals use it to access your computer. You will also learn how to check for spyware infection, differentiate between spyware and adware, and how to get rid of spyware from a device. In our discussion, we will provide an overview of different types of spyware and ways to protect systems against them. At last, we will demonstrate how SentinelOne’s advanced tactics integrate with these methods to provide strong approaches for neutralizing infiltration and preserving data.

What is Spyware?

Spyware is an unauthorized program that runs on a computer, collects information, and relays the information to an attacker or a third-party unauthorized person. As for the question ‘What is spyware,’ the concise definition of spyware points to unauthorized data gathering, including keystrokes or browsing histories. This infiltration commonly operates covertly, monitoring all from the financial login details to the messages and, at times making crucial alterations to the system.

Sometimes, a spyware application hides in other programs that are legal or freeware and people download them without knowing that they are, in fact, installing spyware. Due to the stealth attribute, spyware programs can remain hidden on a computer for weeks or even months, collecting sensitive information for identity theft, espionage, or identity fraud.

Risks and Impact of Spyware

Spyware allows an attacker to easily access passwords, e-mails, and other information, including real-time information about the network. Worryingly, 93% of the components required for typical spyware penetration are either pre-installed or easily enabled on most computers. Now, let us discuss four major effects that infiltration can have on individuals, businesses, and supply chains.

1. Data & Credential Theft: Once spyware is installed, it can scan local files, record keystrokes, or steal credentials entered on a website. The information can then be sold in the black market or used by the attacker for personal benefits. When employees’ passwords or sensitive data get compromised, infiltration is not limited to a specific device, but rather to whole corporate networks. Over time, the stolen credentials could lead to more pervasive sabotage or continued attempts at infiltration of partner ecosystems.
2. Eroded Privacy & Unauthorized Surveillance: For individuals or organizations, infiltration by spyware can mean that their everyday activities can be watched and recorded – including their email correspondence, chat conversations, or location. This long-term spying compromises user privacy, undermines trust within organizations, and damages brand image. In the long term, such infiltration can result in the leakage of significant amounts of personal or corporate information, from trade secrets to private messages. For this reason, several organizations have put in place rigorous scanning procedures and spyware analysis tools to prevent entry points from unverified software.
3. Performance Degradation & System Instability: Since spyware often operates in the background, consuming CPU and memory, infiltration might degrade devices or cause them to crash at random. Some of the advanced tools can change system settings, reduce antivirus efficiency, or make changes to registry keys to hide from spyware detection. These interferences negatively affect productivity and increase helpdesk costs, which add to the infiltration expenses over and above data loss. It is possible to monitor the regular usage of resources and immediately identify the problem to roll back the changes and stabilize the environment.
4. Legal & Financial Repercussions: In the event that personal data is involved, an infiltration discovered late can lead to legal actions such as lawsuits, fines, or even regulatory sanctions. The organization can be held liable for not putting adequate measures in place to prevent such losses by customers or partners. This infiltration can lead to brand degradation, loss of sales, and a possible decline in share price if it escalates into a public scandal. Effective scanning complemented by staff training reduces the likelihood of infiltration success and the penalties that accompany it.

History of Spyware

While infiltration strategies are dynamic in nature, spyware definition has its origin in the early 1980s. Since then, there has been the development of different angles of infiltration across different operating systems and networks. In the next sections, we will define spyware origin and showcase the main milestones in the sophistication of spies and the susceptibility of their targets.

1. Early Browser & Keylogger Emergence: Keyloggers were relatively simple programs that started appearing in the mid-’90s and were capable of capturing passwords typed or chat logs. Attackers spread them through floppy disks or by simply tricking users into downloading them. While these techniques may seem primitive by today’s standards, they introduced a naive user base to extensive privacy violations. The public, being relatively new to cyber threats, had very little understanding or protection against stealthy data exfiltration.
2. Rise of Ad-Supported Software: With the increase in internet usage during the period 2000–2004, software developers began including ad modules in freeware, some of which could be classified as spyware since they would track users’ activity. This infiltration wave relied on new revenue streams, furthering the discussion on user permission and ethical data harvesting. As time passed, advanced modules started gathering more system information, thus transitioning from the usual “adware” into stealth infiltration categories. Regulatory bodies were still far from being able to adapt to the new methods of infiltration.
3. Corporate Espionage & Rootkit-Level Tools: During 2005–2010, infiltration extended beyond home users. Some organizations used seemingly ‘legal’ surveillance tools for detailed tracking without knowing they were also spyware. Some of the infiltration software used rootkit functionality to conceal themselves and processes, making it difficult to detect them. At the same time, Trojan-based espionage became even more popular, new additions to the Trojan’s code base included advanced modules capable of intercepting OS-level calls. While security vendors increased the frequency of scanning solutions, the creators of infiltration enhanced the level of obfuscation and anti-analysis techniques.
4. Mobile & Cross-Platform Infiltration: As the use of smartphones increased between 2011 to 2020, criminals shifted to targeting the Android or iOS platforms to inject malicious applications that were capable of secretly recording calls or even GPS. At the same time, cross-platform infection involved PCs, servers, and IoT devices due to such malware frameworks as multi-architecture. The infiltration complexities compelled security specialists to consolidate scanning, threat intelligence, and user awareness across multiple operating systems. Spyware attacks increased in the world, affecting both consumer segments and business information.
5. State-Sponsored & AI-Enhanced Campaigns: With the increase in the use of advanced infiltration in the past few years (2021–2025), state-backed groups employed the use of spyware detector tools for espionage or strategic sabotage. Advanced techniques such as deep learning, obfuscation, and exploit kits enable attackers to evade traditional scanning solutions. On the other hand, enterprises shifted their focus towards using temporary and portable containers along with strong zero-trust security measures to counter the threats. Spyware remains a potent infiltration threat in 2025 as it continues to fuel an ongoing arms race between attackers and defenders.

What Does Spyware Do?

Spyware is a malicious software that enters a system covertly with the aim of harvesting information, tracking activity, or changing settings without the owner’s knowledge. After being installed, it secretly types, records, searches for files, and monitors messages, including e-mail or chats. Attackers can then sell this information for purposes of identity theft, blackmail, or corporate espionage, thus leading to compromise across various systems.

Since people are more likely to trust programs that are genuine, spyware tends to mimic other programs or bundle itself with other software. The malware may also take advantage of OS vulnerabilities and can integrate itself into the processes running on the system, thus evading detection and constantly stealing information.

Difference Between Spyware and Adware

Though both types of threats involve unauthorized data gathering, spyware is often designed to penetrate deeper into the system, gaining access to such things as login information, OS information, and personal correspondence. Adware, on the other hand, is more oriented toward flooding the user with advertisements, pop-ups, or even forcing them to visit affiliate sites. Still, the difference between the two is not always distinct: some of the ad modules turn into partial spyware if they collect more personal information than stated.

In short, infiltration with adware is mainly for advertising and generating revenues, and infiltration with spyware is what enables hackers to steal information, such as credit card details or company secrets. Despite this, the likelihood of infiltration from adware is still high if it causes the system to have vulnerabilities or change its security settings. However, the first priority is given to spyware removal as it directly intrudes into user and organizational privacy and intellectual property.

Adware often also remains persistent, constantly popping up with new windows or banners with advertisements, while spyware is more discreet. Adware-based infiltration can be annoying to staff or disruptive to productivity, but it does not ransack through files or send sensitive information to the attackers. For companies that have not clearly understood what is a spyware and how it affects the systems, in simple terms, spyware can linger dormant for a long time before it performs a more massive act of espionage or sabotage.

Another difference is in the removal of the infection, while adware can be easily uninstalled if detected, spyware can install rootkit-like features or record keystrokes at the kernel-level. Essentially, both types of infiltration call for effective scanning capabilities, although the harm brought by stealthy spyware infiltration is much greater than that caused by ad-driven nuisances in terms of severity and data theft.

Types of Spyware

As infiltration tactics have broadened, types of spyware have also evolved to fit certain data-gathering goals or infiltration approaches. It is easier to understand the infiltration routes from these categories and see what measures can be taken to prevent them. In the following section, we analyze five key types of threat actors, each having different tactics and capabilities of escalation.

1. Keyloggers: A keylogger records all the activities that are performed on an infected computer, including login details and personal messages. As it takes place in the early stages of the attack process, infiltration provides the attacker with direct access to user behaviors, credit card numbers, or emails. This information can be sold by attackers or used to perpetrate espionage or identity fraud. Stringent scanning and short-term usage make it difficult for intruders to achieve infiltration as no processes are left behind to monitor the typed information.
2. Adware: While not as covert as spyware, adware inundates the screen with pop-ups and banners or directs a user to undesired websites. Some infiltration tactics take adware to a higher level, stealing partial user information or the OS version for advertising purposes. In earlier expansions, it can become more complex adware, which ties espionage to brand identity theft. Removing or scanning potentially dangerous add-ons usually helps to stop infiltration in its early stages.
3. Trojans: A Trojan is a type of virus that disguises itself as an apparently useful program, but it contains hidden attributes, such as data stealing or remote control. This type of attack works by exploiting the user’s trust and opens a file that might turn into an infiltration that could further lead to sabotage. Some Trojan-based spyware contains rootkit modules, which hook OS calls in order not to be detected. Implementing ephemeral usage, real-time scanning or user caution significantly reduces the rate at which Trojan penetrates the system.
4. System Monitors: These infiltration tools collect extensive OS information such as login activities, application usage, or connected gadgets. Like keyloggers, they can also monitor network packets or memory usage, providing infiltration logs to criminals for espionage. In enterprises, infiltration with system monitors may provide information that can be used to stage specific attacks or blackmail. The strict permission controls, the use of an ephemeral environment, and the advanced scanning make it difficult for these stealthy watchers to infiltrate.
5. Tracking Cookies: While not as intrusive as Trojan viruses, tracking cookies may collect the history of the user’s browsing session, site preferences, and behavior during different sessions. Attackers use these cookies to create user profiles and sometimes sell them. In the long run, infiltration at scale can compromise large amounts of data for more sophisticated infiltration or identity theft. Measures such as strict cookie policies, short browsing sessions, or daily scanning can go a long way to lowering infiltration success from these tiny but relentless trackers.

How Does Spyware Work?

All spyware, regardless of the way in which it gains access, has a common goal to gather information or utilize the resources of the system without the consent of the owner. It becomes invisible and sneaks into the operating system level and hence continues to operate undetected for espionage or making money. There are four key ways how spyware infiltration works in today’s environment:

1. Code Injection & Stealth Loading: Criminals place malware in genuine software installers, PDF files, or droppers like Trojan programs. After its initial execution, infiltration code enters into system processes or registry to make sure it runs again after booting up. Infiltration uses new hooking techniques that cannot be detected by the antivirus software. Temporary environment usage or forced code signing makes infiltration challenging for the intruder.
2. Kernel or API Hooking: The advanced level of stealth involves spyware to hook low-level kernel calls or standard application programming interfaces. This way, it captures information such as keystrokes or network traffic before OS security layers can block them. This kind of infiltration makes it almost impossible to detect by the user since criminals can spend a lot of time spying on the victim. Using a temporary memory check or a specific type of intrusion detection stops the intruder at these deeper levels.
3. Obfuscation & Anti-Debug Tricks: Because scanning solutions search for specific patterns, infiltration code usually obscures strings, reorders logic, or uses anti-debug checks. Some infiltration also utilizes packers or encryption wrappers that can only be decrypted at runtime and are, therefore, not easily detected. These illusions make it almost impossible to standard scan, thus keeping infiltration concealed. Using a real-time or exclusively behavioral approach to answer spyware warnings can still help identify some processes or resource utilization as suspicious.
4. Data Exfiltration & Transmission: After infiltrating logs or credentials, infiltration sends them to an attacker’s command-and-control server. Some infiltration campaigns are carried out in such a manner that data is released progressively so that it does not cause disruptions on the network. Some attackers might exfil large files at night or during weekends to avoid being easily noticed by others. Monitoring of the network and the use of temporary credentials or zero-trust concepts can slow the infiltration from getting worse without being noticed.

Signs That Your Device Is Infected with Spyware

When infiltration is detected at the early stage, these signs will help to prevent further infiltration that may lead to a more serious sabotage or data theft. In most cases, infiltration modules are concealed professionally, but there are signs that can reveal them. Here are five signs of spyware activity, with suggestions to indicate that spyware may be at work:

1. Unexplained System Slowdowns: Even if there are few other programs running on the system, if the CPU usage or the memory usage shoots up, then it is likely to be a spyware. Despite the fact that spyware programs are designed to be concealed in the system, they are still capable of using the system’s resources. The expenses can be properly tracked and monitored to ensure that there is a check on the intruders and that the early signs of these infiltrations are noticed.
2. Frequent Crashes or Error Messages: Some of the infiltration processes may interfere with operating system operations, hence leading to random shutdowns. Some of them alter registry keys or OS calls and thus threaten the stability of the system. This means that when there are several mistakes that cannot be explained, then there is a need to scan the environment thoroughly.
3. Mysterious Network Activity: Spyware may upload logs at certain intervals and without user consent to other servers. Such outgoing traffic as may be detected by a firewall could be due to data exfiltration by infiltration. Businesses can also use some tools in a network to detect suspicious connections, including network scanners or solutions such as SentinelOne Singularity™.
4. Appearance of Unknown Toolbars or Apps: Some spyware installs other ads or other unwanted programs, such as managers. Some of the signs that may be visible can also be attributed to infiltration, including the appearance of questionable icons or unauthorized changes. Unauthorized changes and suspicious icons could be signs of infiltration. The problem might not be addressed by manual deletion since there might be deeper roots to the issue.
5. Modified Security Settings: Malware notifications that are turned off or a disabled firewall may indicate tampering by the infiltrator. When it comes to the attacker’s activity, they need to get an unimpeded view of the data they are after. Such changes normally accompany infiltration, and that is why any unauthorized changes signify that infiltration has begun.

How to Detect and Remove Spyware?

Regardless of its appearance on individual gadgets or company networks, early identification followed by elimination is relevant. With scanning solutions and timely actions, infiltration angles are reduced to a minimum. Here are five important procedures that combine the discovery of infiltrations and the elimination of permanent spyware:

1. Use a Trusted Spyware Scanner: Some spyware is designed to look for specific signatures or other types of system calls that the malware might generate. They identify and organize the modules based on the patterns of infiltration that they have in mind. It is important to update the scanner as often as possible to detect new types of infiltration that may be developed.
2. Boot in Safe or Recovery Mode: Some infiltration processes prevent the normal uninstallation process from operating under the standard OS mode. Because booting a limited environment is not possible, there is no auto-launch of infiltration. This approach also assists scanning tools to be more efficient in eradicating infiltration code.
3. Update All Security Patches: When a system is outdated, it provides criminals with infiltration angles. System and application updates fix some of the threats’ entry points that infiltration might use. Ephemeral use or forced versioning can be implemented to avoid recurring infiltration.
4. Check for Rootkit-Like Behavior: In the case of infiltration modules running at the kernel, the standard scanning may not work. Some programs are rootkit detectors, which can uncover the intrusion, and others are for advanced memory analysis. It becomes necessary to clean and reinstall the operating system if the intrusion goes deeper than it should.
5. Reset Credentials & Monitor Logs: Criminals are likely to still possess the passwords after the infiltration process has been executed. Personnel or staff should change all the necessary logins as soon as possible. Monitoring in real-time helps to prevent its recurrence or shift to the remaining accounts.

Real-World Examples of Spyware Attacks

Spyware infiltration is used globally, whether for corporate espionage or the surveillance of journalists. The following section discusses four cases of infiltration scale, victims, and possible repercussions. All emphasize how criminals leverage brand trust or system loopholes to harvest information surreptitiously.

1. Microsoft Breach & Source Code Theft (March 2024): In the previous year, hackers affiliated with two Russian hacking groups allegedly stole Microsoft source code through sophisticated intrusion. These hackers obtained internal network entry points after a predatory attack a year before. Past year, with an increase in the use of “password spray” attacks, the infiltration volume increased, with criminals focusing on executives. Microsoft did not reveal more details, however, such a large-scale infiltration demonstrates that spyware is still effective for code theft and infiltration expansion.
2. Pegasus Spyware on Russian Journalist’s iPhone (September 2023): A journalist from the Russian online media outlet Meduza found out that his iPhone had been compromised by Pegasus, a spyware application. The infiltration took place in Germany, which is the first known use of Pegasus against a high-profile Russian person. Although it is unclear who was behind it (Latvia, Estonia, or other countries that had prior experience with Pegasus), this operation shows that hostile actors can exploit spyware to disrupt communications in any field. The purpose of the infiltration is still unknown, which underlines the covert nature of such global espionage.
3. Vietnamese Hackers Targeting Journalists & Politicians (October 2023): In a campaign designed for top-tier snooping, Vietnamese hackers tried to compromise the phones of journalists, UN representatives, and members of the US Congress. The malware was designed to intercept and steal calls and messages from the compromised devices. These attempts were made at a time when Vietnam was in negotiation with America to contain the rising influence of China in the region. Security specialists note how intrusion progresses from the level of particular gadgets to the top of intelligence objectives.
4. Chinese Hackers Compromise Philippine Government Networks (November 2023): Infiltration groups began launching phishing emails in August 2023 and successfully injected code into the Philippine government’s systems. They monitored the official activities and created infiltration routes to steal important data. This infiltration demonstrates how advanced criminals use e-mailing deceptions to disrupt or gather information at the governmental level. As infiltration of the network is believed to have been conducted for several months, the incident emphasizes the importance of early detection and effective countermeasures.

Best Practices to Prevent Spyware Infections

From training users to sophisticated threat intelligence, organizations can incorporate layered security measures that make it difficult for attackers to penetrate through. Here are five spyware prevention strategies explained in three statements each to help reduce infiltration in various contexts:

1. Keep Software & OS Updated: Ensure that your operating system, web browser, and other frequently used applications are updated to close known vulnerabilities that would allow criminals to take advantage of them. It is also important to configure automatic updates so that patching can be done automatically and not much time is wasted.
2. Install Only Reliable Anti-virus and Anti-spyware Software: Use sophisticated anti-virus and anti-spyware programs that contain up-to-date signatures to identify intrusions and processes that might be spyware dangerous, particularly new ones. Integrate anti-malware scanning based on its signatures with heuristic checks in real-time to provide more protection.
3. Limit Administrator Access & Implement Zero Trust: Restrict administrative access to avoid the situation when a malicious user gains access to all the accounts and controls the entire network. Introduce a zero-trust architecture that uses multi-factor authentication and denies access to unauthorized users to prevent penetration and disruption.
4. Teach Your Employees About Phishing and Social Engineering: Organize periodic training sessions to make the employees aware of different scams, social engineering techniques, and other signs of infiltration. Implement measures to enhance the safe use of email and encourage reporting when something wrong is observed to ensure early intervention.
5. Segment Networks & Monitor Traffic: Ensure that your network is divided into segments so that the intruders cannot move from one part of the network to the other and affect the critical systems. Keep track of the network traffic in real-time and identify any data flow or port that is suspicious to help contain the compromised zones immediately.

Mitigate Spyware Attacks with SentinelOne

SentinelOne’s security platform uses advanced analytics and machine learning to identify and investigate potential threats.

SentinelOne Singularity™ Endpoint is a great anti-spyware solution due to the advanced capabilities it offers organizations. It is designed to provide instant protection against spyware and other forms of malicious items so that the organization can achieve complete security over all its assets. Dynamic device discovery automatically finds and protects network-connected non-managed endpoints, eliminating all possible entry points for attackers.

SentinelOne can gather telemetry data and workflows coming from your organization’s estate to improve visibility and gain actionable control over enterprise endpoints. It can extend its endpoint protection and provide security analysts with real-time insights that help make crucial business decisions. SentinelOne can quarantine and isolate spyware threats live and remediate them. Its platform offers the ability to roll back unauthorized changes and restore the infrastructure to previous and safer states.

SentinelOne’s Offensive Security Engine™ with Verified Exploit Paths™, Storylines™ technology, Purple™ AI, and other features gives you all the tools you need to fight against modern spyware threats. It can also protect your employees from insider attacks, phishing, social engineering, ransomware, and malware.

To learn more, book a free live demo.

Conclusion

Spyware, which dates back to the early 1990s with keyloggers, remains a persistent threat that has been growing and spreading across sectors in 2025. Thus, knowledge about what is spyware, its history, the stages of its infiltration, and the proper measures to take help your team to recognize the signs of infiltration and counter it. Scanning, user awareness, and segmented architectures together make it difficult for infiltrators to gain access, while short-term usage models guarantee that any remaining processes cannot establish themselves. Most importantly, cyclical review of suspicious logs and changes in the scanning thresholds prevent infiltration angles from sneaking back.

As infiltration tactics evolve, comprehensive solutions such as SentinelOne incorporate threat intelligence and response and decrease the time for infiltrators to penetrate and cause further damage. Regardless of whether the criminals switch from using phishing emails with links to the use of attachments containing Trojans or whether they take advantage of zero-day vulnerabilities, SentinelOne steps in and intercepts malicious tasks before the infiltration goes out of control.

Ready to fuse AI-driven defense with your anti-spyware strategy? Combine SentinelOne with your layered defense approach to infiltration and have rock-solid security across your environment.