Effectiveness
Heuristic analysis is capable of detecting many previously unknown viruses and new variants of current viruses. The effectiveness is fairly low regarding accuracy and the number of false positives. Since heuristic analysis operates on the basis of past experience (by comparing the suspicious file to the code and functions of known viruses), it is likely to miss new viruses that contain previously unknown methods of operation not found in any known viruses.
As new viruses are discovered by human researchers, information about them are added to the heuristic analysis engine, thereby providing the engine the means to detect new viruses.
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