There are many examples of good security practices that are not followed by all or most users of the internet. These leave people open to attacks from viruses or from people who are conducting "phishing."
Some of the most obvious of these practices are having good antivirus protection and a firewall on all computers. The antivirus protection should protect against spyware, viruses, and other types of malware. It is also important to get updates to your operating system as they are made available by the manufacturer. These updates close vulnerabilities that cybercriminals can use to try to take control of your computer.
Finally, it is also a good idea to have strong passwords. These should be a mix of capital and lower case letters and should have numbers as well.
Many people do follow these rules, but there are still large numbers who do not.