Viruses, spyware and other malicious software can stop your computer working properly, can delete or corrupt your files and can allow others to access your computer and your information.
There are many ways in which your computer can be infected-clicking on website links, downloading infected files from the internet or opening infected email attachments.
Anti-virus and anti-spyware software act like gatekeepers by monitoring incoming and outgoing traffic between your computer and the Internet and scanning and checking the files you download or open. They can detect, quarantine or remove suspicious files to keep your computer clean and your information secure.
- Install and activate anti-virus and anti-spyware software. Most computers bought in the last few years have trial software already installed on them. When this trial software expires, ensure you renew the subscription or find an alternative service.
- Set your security software to automatically update. New viruses and spyware are created every day, so it is important that your software is up-to-date and can detect new threats.
- Install a firewall. A firewall will monitor information going in and out of your computer and block unauthorised activity.
- Don't buy security software in response to unexpected pop-up messages or emails, especially ads that claim to have scanned your computer and detected malware. Some scammers distribute malware disguised as anti-spyware software.
- Check your computer is not already infected. Run your anti-virus software to check. If it is infected, delete the infected files.
- Keep yourself informed about the latest online safety and security risks. Subscribe to email notification services that keep you informed about the latest online safety and security risks and solutions. See our Alert Service.
On this page
- What is 'malware' and how does it affect your computer
- How does your computer become infected with malware
- How to prevent spyware from getting onto your computer
- Where to get anti-virus and anti-spyware software
- What if your computer is already infected
Fact sheets and resources
- Secure computing checklist (PDF, 113 KB)
- Free security software (PDF, 616KB)
- Web threats - what are they and what you can do to protect your computer and information? (PDF, 251KB)
- Setting up Automatic Updates in Windows XP (PDF, 135Kb)
- You suspect your computer is infected with malicious software - what should I do? Part 1, Part 2, Part 3
Spyware Quiz - Do you know how to take care of spyware? Take the quiz now and learn more!
What is 'malware' and how does it affect your computer
Malware-short for 'malicious software'-is the term often used to refer to any type of malicious code or program that is used for monitoring and collecting your personal information (spyware) or disrupting or damaging your computer (viruses and worms).
The term spyware is typically used to refer to programs that collect various types of personal information or that interfere with control of your computer in other ways, such as installing additional software or redirecting web browser activity.
Examples of spyware include:
A keylogger is a program that logs every keystroke you make and then sends that information, including things like passwords, bank account numbers, and credit card numbers, to whomever is spying on you.
A Trojan may damage your system and it may also install a 'backdoor' through which to send your personal information to another computer.
Viruses and worms
Viruses and worms typically self-replicate and can hijack your system. These types of malware can then be used to send out spam or perform other malicious activities and you may not even know it. Both can use up essential system resources, which may lead to your computer freezing or crashing. Viruses and worms often use shared files and email address books to spread to other computers.
How does your computer become infected with malware
Most spyware is installed without your knowledge. It often gets onto your computer through deception or through exploitation of browser vulnerabilities.
- Spyware can come bundled with other software. When you download a program, the spyware can be downloaded and installed at the same time.
- Some spyware infect a system through security holes in the Web browser or in other software. When the user navigates to a Web page controlled by the spyware author, the page contains code which attacks the browser and forces the download and installation of spyware.
- Be wary of USB sticks from unfamiliar or untrustworthy sources, for example those given away at conferences, trade shows, or in promotional packs. These devices may contain malicious software, which could cause severe damage to your computer or compromise your personal information.
- Some "rogue" spyware programs masquerade as security software.
- Worms can also be used to install spyware on your computer.
How to prevent spyware from getting onto your computer
Develop good security practices. You need to have Internet security measures in place and have an understanding of how your computer works.
- Install anti-spyware and anti-virus software and set it to automatically check the product website for updates. This will ensure that your computer is protected against the latest viruses and spyware.
- Install a firewall. It will prevent unauthorised access to your computer and the installation of spyware on it. Some firewalls can also prevent information being taken from your computer and sent to someone else.
- If you must use a USB stick from an unfamiliar source, you should always scan the USB stick for viruses or other malware before accessing any of its content. You should also disable the autorun function, which is commonly enabled on the Microsoft Windows operating system. This will lessen the risk that any malicious software that may be on the USB stick, will automatically start when you connect it to your computer.
- Keep yourself informed about the latest security threats and solutions. You can sign up for the free Stay Smart Online Alert Service from this website. Alternatively, your anti-virus software vendor may have an email alert system. Look for a 'keep informed' tab or section on the software's main screen.
- Be cautious about opening emails from unknown or suspicious sources. Look at the sender of the email as well as the body and the subject of the email. Do not open email attachments or click on hyperlinks in these emails. You should install spam filters to minimise the amount of spam you receive.
- Set your anti-virus software and anti-spyware software to automatically scan incoming email.
- Be wary when exchanging files even with colleagues or friends. Scan the files before you install them or run them on your computer.
- Never click on an 'Agree', 'Ok' or 'No' button to close a window on a suspicious website or pop-up. This can launch spyware onto your computer. Instead, click the red 'X' in the corner of the window to close the window.
Where to get anti-virus and anti-spyware software
Most computers bought in the last few years have trial anti-virus and anti-spyware software already installed on them. There are also many commercial and free products available.
For a list of non-commercial anti-virus and anti-spyware software and more information on protecting you computer, please see:
If you have a legitimate Microsoft Windows licence you can install Windows Defender anti-spyware free of charge.
Once you have installed your security software, make sure it is always turned on. When the subscription is due, renew your software or replace it with a similar product.
Fake anti-virus and anti-spyware software
Some scammers distribute malware disguised as anti-spyware software. Don't buy software in response to unexpected pop-up messages or emails, especially ads that claim to have scanned your computer and detected malware. These messages aim to trick you into believing your computer is already infected, and that purchasing the software will help get rid of it.
Do your research first and choose products that are reputable and well known. Computer magazines often review security software and can provide useful information about features, costs and limitations to help you make an informed choice.
What if your computer is already infected
Check your computer is not already infected with spyware. The following signs may indicate that spyware is on your computer:
- your web browser starts on a different homepage than it normally would
- your computer's performance is slower than normal
- random error messages appear
- new toolbars and icons have been installed, or
- if you have a dial-up internet connection, you may find unauthorised premium rate phone calls on your bill.
To check if your computer is infected with a virus and remove it, run your anti-virus software and follow the instructions. You should run your anti-virus software at least once a week.