This can happen when a lot of people share the same external IP. For example, behind campus networks and the like.
If this sounds like your situation, then either try waiting a while for the IP to (hopefully) be removed from the blacklist, or use a proxy to access the website.
If this doesn't sound like it, i.e. you're using a small home network, then you can try obtaining a new IP address (assuming you have a dynamic IP account with your ISP) by powering down and powering back up your modem - whether it's Cable, ADSL or otherwise.
If you're concerned about malware (very unlikely - both because it's uncommon on Linux, and also because it's extremely unlikely any malware would choose to repeatedly hit Google's search page), then you might choose to use a tool like Wireshark to monitor outgoing packets. Or, even better, run Wireshark on another PC on your home network using promiscuous mode. However, like I say, that's extremely likely to be a waste of your time.