Why do I need to finish a CAPTCHA?
Completing the CAPTCHA proves you are a human and offers you temporary access to the web property.
What can I do to prevent this in the future?
If you are on an individual connection, like in the house, you can run an anti-virus scan on your gadget to ensure it is not contaminated with malware.
If you are at a workplace or shared network, you can ask the network administrator to run a scan across the network looking for misconfigured or contaminated devices.
Another way to avoid getting this page in the future is to utilize Personal privacy Pass. Have a look at the browser extension in the Chrome Web Store.