I guess you use Chrome, right? Or Google is your default search engine? This is copy-paste from a Chrome community site:
ad.doubleclick.net is not malware. It’s an advertising link retuned by Google to redirect your browser to the desired site. DoubleClick is Google’s advertising company. They use this referral scheme in order to track your browsing habits (to learn what words you searched for that led you to click on their ad), and for Google to collect a referral bonus for displaying such a good advertisement that you clicked on it. You are just seeing an error because your browser can’t get to their servers.
The error you’re seeing is because you have ad.doubleclick.net blocked in your computer somehow. You may be browsing using a “proxy” that is blocking that address; your router or firewall may be blocking the doubleclick.net domain; you may have blocked doubleclick in your hosts file; you may have installed a DNS ad blocker like pi-hole; or maybe you have installed any number of tools that might block these requests.
They might not call it malware, but IMHO it is. Wanna get rid of it? Delete/uninstall Chrome. I have two browsers of choice: FireFox and Edge Chromium. If you like the look and feel of Chrome, go for Edge Chromium.
Cheers,
Priller