1. A method of string analysis using a computer-based comparison tool, comprising: identifying, using the computer-based comparison tool, a plurality of target strings; representing each of the plurality of target strings as one or more target features; compiling, using the computer-based comparison tool, an index corresponding to the target features, wherein the index comprises a mapping for each target feature to each of the plurality of target strings containing the target feature; receiving, using the computer-based comparison tool, a source string; representing the source string as a plurality of source features; determining a portion of the target strings for which a similarity metric is to be calculated, wherein the portion of the target strings comprises less than the entirety of the target strings; and calculating, using the computer-based comparison tool, a similarity metric for the source string relative to the portion of the plurality of target strings, wherein the similarity metric is at least partially based on commonality between the target features and the source features.