I have noticed items appearing in my internet history that I have not visited, including medical websites, news websites, websites about home improvement e.t.c. There are also several entries which simply appear as a string of numbers, like an IP address. I am the only person using the computer, and I can see new items being added to the history that the browser has not been on. It only seems to affect Internet Explorer, and not any other browser. Is this caused by malware, or is there another explanation?