Some particular malwares infect the user computer and try to send traffic to Google through a small number of intermediary servers called “proxies.” Google found some unusual traffic while performing routine maintenance on one of their data centers.
After Google is collaborating with security engineers at several companies that were sending this modified traffic, they determined that the computers exhibiting this behavior were infected with a particular strain of malicious software, or “malware.”
Today, if anyone has these type of malware , they will notify as your system is infected while searching in google.
Source: google Official Blog
