Spyware is malware that secretly monitors a device and collects information without the user’s knowledge or consent. Spyware gathers data such as keystrokes, browsing history, login credentials, and files, then sends it to a third party. The Cybersecurity and Infrastructure Security Agency (CISA) and security vendors including Malwarebytes and Kaspersky classify spyware as a malware category that targets confidentiality.
This article defines spyware, lists the types including keyloggers, infostealers, tracking cookies, stalkerware, and adware-spyware, explains how spyware spreads, describes what it steals, lists the signs of infection, and sets out detection, removal, and prevention. Each section states one part of the topic and connects it to the covert data collection at the center of the definition. The result is a complete account of what spyware is, what it collects, and how to detect, remove, and prevent it.
What Is Spyware?
Spyware is malware that covertly monitors a device and collects information such as keystrokes, browsing activity, and credentials without the user’s consent. Spyware targets confidentiality, gathering data in the background and sending it to a third party. The defining traits of spyware are listed below:
- Covert operation runs in the background to avoid the user’s notice.
- Data collection captures keystrokes, browsing history, credentials, and files.
- Unauthorized transmission sends the collected data to a remote party.
- No consent defines spyware, since the user never agrees to the monitoring.
Spyware is one category within the broader set of malicious software described in the overview of malware. Spyware targets confidentiality by stealing information, distinguishing it from ransomware, which targets availability by encrypting data.
What Are the Types of Spyware?
The types of spyware are keyloggers, infostealers, tracking cookies, stalkerware, and adware-spyware. A spyware type is defined by the kind of information it collects and how it operates. The types are listed below:
- Keyloggers record every keystroke to capture passwords, messages, and other input.
- Infostealers extract stored passwords, browser data, and files from a device.
- Tracking cookies follow browsing activity across websites, often for profiling.
- Stalkerware monitors a specific person’s device, including location and messages.
- Adware-spyware combines advertising with tracking of browsing behavior.
A keylogger is a spyware type that records keystrokes, detailed in the guide to keyloggers. Adware-spyware overlaps with advertising malware, explained in the guide to adware, since both track browsing while displaying or collecting data.
How Does Spyware Spread?
Spyware spreads through bundled software, deceptive downloads, phishing email, malicious websites, and trojans. A spread method is the path spyware uses to reach a device. The main methods are listed below:
- Bundled software hides spyware inside free programs the user installs.
- Deceptive downloads disguise spyware as a useful tool or update.
- Phishing email delivers spyware through a malicious attachment or link.
- Malicious websites install spyware through drive-by downloads.
- Trojans carry spyware as a hidden payload inside disguised software.
Bundled software and deceptive downloads are common spyware delivery methods, according to Malwarebytes. A trojan often carries spyware as its payload, the disguise mechanism explained in the guide to the trojan horse.
What Does Spyware Steal?
Spyware steals keystrokes, login credentials, browsing history, financial data, and stored files. The stolen information serves identity theft, fraud, and further attacks. The data spyware targets is listed below:
- Keystrokes reveal passwords, messages, and search queries as the user types.
- Login credentials grant access to accounts and services.
- Browsing history exposes habits and interests for profiling or fraud.
- Financial data includes banking details and payment card numbers.
- Stored files contain documents, photos, and other personal data.
Stolen credentials and financial data enable identity theft and fraud, according to CISA. Spyware that captures banking details, sometimes called a banking trojan when delivered by deception, targets financial accounts directly.
What Are the Signs of Spyware?
The signs of spyware include slow performance, frequent pop-ups, high data usage, changed browser settings, and unfamiliar programs. A symptom is an observable change that suggests spyware is running. The common signs are listed below:
- Slow performance appears as the device lags from spyware running in the background.
- Frequent pop-ups indicate adware-spyware displaying advertisements.
- High data usage reflects spyware transmitting collected information.
- Changed browser settings include a new home page or unexpected toolbars.
- Unfamiliar programs appear that the user did not install.
These signs suggest spyware, though well-designed spyware hides to avoid detection, according to Kaspersky. A scan with anti-malware software confirms whether spyware is present when symptoms appear, since some spyware shows no visible signs.
How Do You Detect and Remove Spyware?
Spyware is detected and removed by running a full anti-malware scan, deleting detected threats, resetting browser settings, and changing compromised passwords. Removal eliminates the spyware and limits the damage from stolen data. The steps are listed below:
- Run a full scan with reputable anti-malware software to detect spyware.
- Delete or quarantine the detected spyware and restart the device.
- Reset browser settings to remove changed home pages and toolbars.
- Change passwords for accounts that the spyware may have captured.
- Enable monitoring for suspicious account activity following the infection.
A full anti-malware scan removes most spyware, and changing passwords limits the damage from stolen credentials, according to Malwarebytes. The detailed removal procedure appears in the steps to remove malware from a PC, and the detection methods behind a scan are explained in the guide to how antivirus software works.
How Do You Prevent Spyware?
Spyware is prevented by installing software only from trusted sources, applying updates, using antivirus, declining bundled programs, and avoiding suspicious links. A preventive measure reduces the chance spyware reaches a device. The core defenses are listed below:
- Trusted sources limit downloads to official stores and vendor sites.
- Software updates patch the vulnerabilities spyware exploits.
- Antivirus software detects and blocks known spyware before it installs.
- Declining bundles avoids the extra programs packaged with free software.
- Link caution avoids the phishing messages that deliver spyware.
Installing software only from trusted sources blocks the bundled and deceptive downloads that carry spyware, according to CISA. Antivirus software adds a detection layer whose value is set out in the explanation of why antivirus matters.
How Does Spyware Work?
Spyware works by installing silently, running in the background, collecting data, and transmitting it to a remote server controlled by the attacker. Spyware follows a sequence from installation to data exfiltration. The stages are listed below:
- Installation places the spyware on a device through a bundle, download, or trojan.
- Background execution runs the spyware without a visible window or notification.
- Data collection records keystrokes, browsing, credentials, and files.
- Transmission sends the collected data to a remote server.
Spyware operates silently to maximize the data it collects before detection, according to Malwarebytes. The transmission stage produces the high data usage that often signals an infection, since the spyware continuously sends collected information.
What Is the Difference Between Spyware and Adware?
Spyware secretly collects information to steal data, while adware displays advertisements to generate revenue, though adware-spyware combines both. The difference lies in the primary goal. The distinctions are listed below:
- Spyware targets confidentiality, stealing data for fraud and identity theft.
- Adware targets revenue, forcing advertisements onto the user.
- Adware-spyware tracks browsing to target advertisements, blending both goals.
- Detection differs, since adware is visible while spyware hides.
Adware is more visible than spyware, but adware that tracks browsing crosses into spyware, according to Kaspersky. The advertising malware category is detailed in the guide to adware, which explains where tracking turns adware into a privacy threat.
What Is Stalkerware?
Stalkerware is spyware installed to monitor a specific person’s device, tracking location, messages, calls, and activity without consent. Stalkerware differs from broad spyware by targeting one individual. The traits of stalkerware are listed below:
- Targeted monitoring watches one person rather than collecting data broadly.
- Location tracking reports the device’s position to the installer.
- Message and call access exposes private communications.
- Covert installation often requires physical access to the device.
Stalkerware raises legal and safety concerns because it monitors a person without consent, according to CISA and the Coalition Against Stalkerware. Anti-malware tools increasingly detect stalkerware, and a full scan helps identify monitoring software installed on a device.
What Are Examples of Spyware?
Well-known spyware examples include Pegasus, FinFisher, and the Zeus keylogger component. A spyware example shows how the category operates in a real incident. The notable examples are listed below:
- Pegasus is surveillance spyware documented for monitoring mobile devices, including messages and location.
- FinFisher is commercial surveillance spyware sold for monitoring computers and phones.
- Zeus included keylogging that captured banking credentials from infected devices.
- CoolWebSearch was early adware-spyware that hijacked browser settings and tracked activity.
Pegasus, documented by security researchers including Citizen Lab, showed how spyware reaches mobile devices to monitor communications. A keylogger component, as in Zeus, captures input directly, the mechanism detailed in the guide to keyloggers.
Can Spyware Affect Phones?
Spyware affects phones as well as computers, infecting smartphones to track location, messages, calls, and app activity. A mobile infection vector is the path spyware uses to reach a phone. The mobile spyware facts are listed below:
- Malicious apps carry spyware disguised as legitimate applications.
- Phishing links deliver spyware through text messages and email on a phone.
- Stalkerware apps monitor a target’s phone after physical installation.
- Permission abuse lets spyware access location, microphone, and camera.
Mobile spyware reaches phones through malicious apps and phishing links, according to Malwarebytes, and abuses granted permissions to access sensitive sensors. Installing apps only from official stores and reviewing app permissions reduces the chance of mobile spyware infection.
Key Takeaways
- Spyware covertly monitors a device and collects information without consent.
- Types include keyloggers, infostealers, tracking cookies, stalkerware, and adware-spyware.
- Spyware spreads through bundled software, deceptive downloads, phishing, and trojans.
- Spyware steals keystrokes, credentials, browsing history, financial data, and files.
- Signs include slowdowns, pop-ups, high data usage, and changed browser settings.
- Removal uses a full scan, threat deletion, browser reset, and password changes.
What is spyware in simple terms?
Spyware is malware that secretly monitors a device and collects information such as keystrokes, browsing history, and credentials without the user’s consent, then sends the data to a third party.
What are the types of spyware?
The types of spyware are keyloggers, infostealers, tracking cookies, stalkerware, and adware-spyware. Each is defined by the kind of information it collects and how it operates.
What does spyware steal?
Spyware steals keystrokes, login credentials, browsing history, financial data, and stored files. The stolen information serves identity theft, fraud, and further attacks on the victim’s accounts.
What are the signs of spyware?
Signs of spyware include slow performance, frequent pop-ups, high data usage, changed browser settings, and unfamiliar programs. Some spyware hides and shows no visible signs.
How do you remove spyware?
Remove spyware by running a full anti-malware scan, deleting detected threats, resetting browser settings, and changing passwords for accounts the spyware may have captured.
How do you prevent spyware?
Prevent spyware by installing software only from trusted sources, applying updates, using antivirus, declining bundled programs, and avoiding suspicious links and attachments.
Last Thoughts on Spyware
Spyware is malware that secretly monitors a device and collects information without the user’s consent. Spyware types include keyloggers, infostealers, tracking cookies, stalkerware, and adware-spyware, and it spreads through bundled software, deceptive downloads, phishing, and trojans.
Spyware steals keystrokes, credentials, browsing history, and financial data, and its signs include slowdowns, pop-ups, high data usage, and changed browser settings, while removal uses a full scan, threat deletion, browser reset, and password changes. Readers can continue with the overview of malware, the guide to keyloggers, the guide to adware, or the overview of cybersecurity.
