Do not ever respond or open e-mails or attachments from unknown and unauthentic sources. Moreover, do not open e-mail attachment even from known sources if it appears to be malicious. 

Use firewalls to secure your computer and networks from hackers and cyber intruders. 

Keep up-to-date with latest security updates and patches for operating systems and other sorts of software.

Rely on hard-to-guess passwords formed by a combination of upper & lower case letters, numbers and special characters. Make sure that your password is at least 8 characters long.

Take timely backup of your data on disks, cloud, or other data storage devices.

Do not share your computer or mobile with strangers. Learn more about file-sharing risks.

Ensure to delete cookies, saved passwords, auto-fills and other data sensitive data from the public systems such as Cyber cafes.

Check for online security on a regular basis. Ensure to reevaluate your system's security when you change your clocks for daylight-savings time.