On Complexity of the Detection Problem for Bounded Length Polymorphic Viruses

The complexity of the virus detection problem has received much attention from researchers over the past years. Using a grammar-based formalism for polymorphic viruses and based on the recognition problem for a fixed grammar we provide two examples of polymorphic engines, corresponding to bounded length viruses, whose reliable detection problem is NP-complete and PSPACE-complete. Thus, by giving an example of a fixed context sensitive grammar whose recognition problem is PSPACE-complete, we show that the detection problem for bounded length polymorphic viruses is not NP-complete as previously believed.