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Metamorphic computer viruses “mutate” by changing their internal structure and, consequently, different instances of the same
virus may not exhibit a common signature. With the advent of construction kits, it is easy to generate metamorphic strains
of a given virus. In contrast to standard hidden Markov models (HMMs), profile hidden Markov models (PHMMs) explicitly account
for positional information. In principle, this positional information could yield stronger models for virus detection. However,
there are many practical difficulties that arise when using PHMMs, as compared to standard HMMs. PHMMs are widely used in
bioinformatics. For example, PHMMs are the most effective tool yet developed for finding family related DNA sequences. In
this paper, we consider the utility of PHMMs for detecting metamorphic virus variants generated from virus construction kits.
PHMMs are generated for each construction kit under consideration and the resulting models are used to score virus and non-virus
files. Our results are encouraging, but several problems must be resolved for the technique to be truly practical. 相似文献
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The presumed-either two-phase commit protocol 总被引:2,自引:0,他引:2
This paper describes the presumed-either two-phase commit protocol. Presumed-either exploits log piggybacking to reduce the cost of committing transactions. If timely piggybacking occurs, presumed-either combines the performance advantages of presumed-abort and presumed-commit. Otherwise, presumed-either behaves much like the widely-used presumed-abort protocol. 相似文献
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