What Is Spyware? Definition, Types, and Protection

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Spyware is a malicious software program placed on a user’s computer without their permission. Once the spyware enters the computing environment, it gathers confidential information and transmits it to third parties and fraudulent organizations in exchange for money. Essentially, any app or program installed without the user’s knowledge is considered spyware.

Spyware is dangerous because even when it’s downloaded for legitimate reasons, it can expose personal information like credit card numbers, login details, and personally identifiable information (PII), enabling data exploitation by bad actors.

How spyware works

To execute a spyware attack, hackers carefully disguise malicious spyware within files and emails. When a user unknowingly clicks on an infected email attachment or opens a pop-up ad, the spyware gets installed onto the device.

Once the spyware is downloaded successfully, it insidiously starts tracking the user’s movement by using several techniques like keystroke loggers, trojans, and system monitors to capture their data and steal their personal information.

The spyware keeps running in the background and covertly tracks user activities without their permission. It notes their personal and financial details, browsing history, and downloads, and secretly relays this information to attackers who use it for their nefarious designs.

Apart from this, spyware can even make configurational changes to the computer and modify the computer’s firewall settings to clear the path for more malware entry.

Types of spyware

Several types of spyware exist. The main types are keystroke loggers, adware, Trojan horses, system monitors, and infostealers.

Keystroke loggers

Keystroke loggers or keyloggers are a form of spyware that records users’ keystrokes and saves the information in a log file. Keyloggers are dangerous because they silently collect all data, such as passwords, user names, account information, and financial details, without the user knowing until it’s far too late.


Adware or advertising-supported software is a common type of spyware that targets victims with pop-up ads. These ads collect personal information about the user and send it to malware developers for mining purposes.

Trojan horses

Trojan horses are malicious programs that camouflage themselves as harmless software and invade your system. Once inside, they take over and start accessing and stealing your personal information. Trojan horses, like remote access trojans (RATs), allow hackers to get unrestricted control of systems and compromise user credentials.

System monitors

System monitors are a dangerous form of spyware that gathers all your browsing data, including all that you do on your computer, like websites visited, chatroom dialogues, emails sent, etc. Like keyloggers, they run in the background covertly, so you don’t even know they’re running.


Similar to other spyware, infostealers enter devices slyly and start collecting information from the user’s computer without their knowledge. However, unlike keyloggers that record info only from keystrokes, infostealers indiscriminately record all data entered on your computer or phone, from your browsing history to your private information, such as passwords and email accounts.

Common issues caused by spyware

While it’s challenging to identify spyware on a device, there are certain warning signs that could point to a spyware infection.

  • Computer is slow or crashes frequently.
  • Device runs out of hard disk space.
  • Anti-malware programs don’t work.
  • Frequent pop-ups appear on your screen.
  • Device overheats.
  • Appearance of browser installations or plugins you didn’t install.

If you start noticing any of these sorts of issues beginning to happen on your device, you should always investigate the cause as quickly and thoroughly as possible.

How to protect devices against spyware

While there’s no definitive way to protect your devices from viruses and malicious software, you can still take measures to keep your devices safe.

1. Be wary of third-party cookies

Although cookies are usually harmless, they can also be used for malicious activities. Malicious cookies spy on your online activities and collect your personal information, which is then sold to other companies or put on the dark web. That’s why several browsers like Firefox and Safari no longer support third-party cookies.

2. Don’t click on untrustworthy attachments

One of the common ways for spyware to get onto computer systems is through phishing attacks. On the surface, phishing attempts look like legitimate messages from trustworthy sources like your bank asking for your login details or your operating system (OS) asking you to download a free update.

To be on the safer side, delete such emails and do not click on their attachments. You can always call your bank or open your OS updater to check independently later.

3. Use strong passwords

Use strong passwords to keep your devices safe from the prying eyes of cybercriminals. Use a separate password for your accounts and ensure they’re a combination of special characters, upper and lower-case letters, and numbers. Avoid using passwords that can be easily guessed, like your birthday or name, and keep changing your passwords every few months.

4. Be careful of pop-up ads

Pop-up ads appear unexpectedly when you visit a website and ask you to take urgent action by clicking on the message. The rule is to never click “agree” or “OK” to close a window, and it’s best not to click the “X” in the corner, either, as that can actually be a part of the pop-up in disguise. The best approach is to close that tab or window entirely from the browser menu.

5. Use an anti-spyware tool

Spyware and other malware can insidiously enter your computer and remain hidden there. Getting rid of them isn’t a simple task, yet a powerful anti-spyware tool can give you real-time defense against malicious software. Anti-malware and anti-spyware software continuously protects your devices from all kinds of malware and viruses.

Top 3 anti-spyware tools

There are a huge number of antivirus and anti-malware tools available today. It’s important that you choose one that is reputable and dependable, as spyware and other malware can enter your system disguised as legitimate software.

Here are three of the best antivirus software to protect your computer from spyware.

Bitdefender Total Security

Bitdefender Total Security is a comprehensive anti-malware tool that uses state-of-the-art cybersecurity technologies to protect against a range of cybersecurity threats. Features include a firewall, VPN, parental control, spam filtering, secure browser (SafePay), system optimizer, and password manager. Pricing starts at $39.99 per year for five devices, and Bitdefender also offers a free version for basic antivirus scanning.


Malwarebytes is an anti-malware and anti-rootkit scanner that scans and removes all malicious software from Android, Mac, PC, and iOS devices. It has an intuitive interface that makes it easy for users to navigate. Quick and easy scans are given by the Hyper Scan mode in Malwarebytes, while the four layers of defense remove viruses effectively. Malwarebytes offers a variety of pricing options for personal and business use, from a free version on up.


Norton is a top-rated anti-malware program that offers the most robust protection against all types of cyber threats. It includes a variety of features such as dark web monitoring, parental protection, webcam protection (for Windows), smart firewall, and more. While Norton doesn’t offer a free version, they do have a huge variety of pricing options starting at $19.99 per year for one device.

Removing spyware in 5 steps

If you suspect your device has been installed with spyware, you can take a few quick steps to mitigate any threats:

  1. First, disconnect from the internet to prevent further damage.
  2. Start your computer in Safe Mode.
  3. Check your computer’s program list for any suspicious files.
  4. Uninstall those files, and after that, reboot the system.
  5. To be extra sure, perform an antivirus scan of the contents of your device. A good and reliable antivirus tool will scan for all possible threats and successfully sanitize the system.

Bottom line: Protecting against spyware

Although not all spyware can gain access to your personal data, you should still protect your devices against a spyware attack. The presence of spyware can not only cause changes to your device but also result in irreparable data loss. Having a clear understanding of spyware and its workings will enable you to implement steps to keep your sensitive data more secure.

We evaluated the best antivirus software for enterprises to protect against spyware and other malware.

Susnigdha Tripathy
Susnigdha Tripathy
Susnigdha Tripathy is a full-time writer and editor based in Singapore, and a regular contributor to Enterprise Networking Planet. She has over 10 years of experience writing, editing, and delivering exceptional content for a variety of international technology brands such as Virtasant, a cloud technology company, and Krista Software, a provider of intelligent automation solutions. She has also appeared in ServerWatch and other industry publications.

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