How do I know that my computer has been attacked by a bot?

Criminals who spread bots want to go undetected. This also applies to the bots that are active on millions of computers worldwide. The first signs of an infestation are a deteriorated Internet or computer speed, unwanted page views and advertising or even that you can no longer access pages with the popular browsers (Internet Explorer, Firefox, Opera). However, infected computers do not necessarily have to show these symptoms. Users often do not notice at all or very late that their computer has become part of a botnet.