1. A method of suggesting custodians subject to a litigation hold, comprising: receiving a set of keywords or queries; identifying, by one or more processing devices, a set of documents relevant to the set of keywords or queries; identifying, by one or more processing devices, one or more custodians associated with one or more documents in the set of documents; and determining a set of one or more candidates for the litigation hold from the identified one or more custodians based upon a comparison of the identified one or more custodians to a known set of one or more custodians relevant to the litigation hold, wherein each of the identified one or more custodians that is external to the known set of one or more custodians is added to the set of one or more candidates, providing, by the one or more processing devices, the determined set of one or more candidates for the litigation hold to a user.