Heuristics attempts to deflect such attacks by unrecognized viruses.
But the results are often incorrect and, depending on the particular program, heuristics can be extremely annoying to users. That was the case recently when I took a look at four leading antivirus programs. No two were alike, and not one of them was ideal. Although each antivirus program operated differently, I evaluated them by the same criteria. The first and most fundamental test was how quickly and thoroughly each contender could scan for viruses.