I have never heard of filtering by keystrokes. Usually this filtering takes place by software such as McAfee in the form of add-on packages that process the data before being allowed to settle inside your computer. These are usually purchased separately and tend to slow your computer down because of the processing involved. Alternatively you can get free packages such as Ad aware which you run post installation and which do not affect the speed..
"+" if you want to definately include the word, "-" if you definately dont want to, and "OR" if you want it to be one of 2 things. & if its a certain phrase, you can put it in quotation marks.