  Word obfuscation or substitution means replacing one word with another word
in a sentence to conceal the textual content or communication. Word obfuscation
is used in adversarial communication by terrorist or criminals for conveying
their messages without getting red-flagged by security and intelligence
agencies intercepting or scanning messages (such as emails and telephone
conversations). ConceptNet is a freely available semantic network represented
as a directed graph consisting of nodes as concepts and edges as assertions of
common sense about these concepts. We present a solution approach exploiting
vast amount of semantic knowledge in ConceptNet for addressing the technically
challenging problem of word substitution in adversarial communication. We frame
the given problem as a textual reasoning and context inference task and utilize
ConceptNet's natural-language-processing tool-kit for determining word
substitution. We use ConceptNet to compute the conceptual similarity between
any two given terms and define a Mean Average Conceptual Similarity (MACS)
metric to identify out-of-context terms. The test-bed to evaluate our proposed
approach consists of Enron email dataset (having over 600000 emails generated
by 158 employees of Enron Corporation) and Brown corpus (totaling about a
million words drawn from a wide variety of sources). We implement word
substitution techniques used by previous researches to generate a test dataset.
We conduct a series of experiments consisting of word substitution methods used
in the past to evaluate our approach. Experimental results reveal that the
proposed approach is effective.
