As the importance of data in our computing systems has increased, number of viruses that may harm its integrity has also increased. It has become very important to detect them, so that we can remove them as well as disinfect the infected files. This paper presents an implementation of a fast signature scanner to detect the viruses. To reduce the scanning time, it uses Boyer-Moore-Horspool (BMH), a fast pattern-matching algorithm. It showed the best performance among commonly used pattern matching algorithms like Boyer Moore and Turbo-Boyer-Moore algorithms. General TermsIntegrity checking technique, Signature scanning technique, Pattern matching problem. KeywordsBoyer-Moore-Horspool (BMH), Boyer-Moore algorithm.