Google (Linux) error message

This one is a new for me, I'm setting up snmpd on my OpenBSD box at home, so I wanted to check something fast regarding the configuration file.
Opened Firefox, on Windows, and went to "google.com/linux"; to my surprise, it came out with the banner on the picture, and a CAPTCHA.
After typing the code on the box, I have been able to navigate to the page with out any problem.
I suspect this might be from a worm on the ISP I'm connecting from.