By keeping an eye on web traffic, Google can spot anomalies, assess where the data is coming from, and warn businesses or users that they are infected.
“We work every day to detect potential abuse of our services and ward off attacks,” said Damian Menscher, security engineer, on the Google blog. “As we work to protect our users and their information, we sometimes discover unusual patterns of activity."
"After collaborating with several companies that were sending this modified traffic, we determined that the computers exhibiting this behaviour were infected with a particular strain of malicious software, or malware.”
The company said it will warn users by displaying a notification at the top of Google search results.
According to Google, the malware in questions caused infected machines to send traffic via proxies and by “taking steps to notify users whose traffic is coming through these proxies, we can help them update their antivirus software and remove the infections”.
Although Google will attempt to notify as many people as possible to the problem, it said users could also visit the Help Centre to check whether their machines were infected.
It is unclear whether this was a one-off notification or whether the company plans to routinely take a more proactive approach to network security issues.
This article originally appeared at pcpro.co.uk