A computer-implemented method for distributing spam signatures may include identifying a set of spam e-mails. The computer-implemented method may also include identifying a plurality of clients, each client in the plurality of clients having received at least one e-mail in the set of spam e-mails. The computer-implemented method may further include identifying at least one mailing list by identifying at least one group of clients within the plurality of clients that have received a subset of the set of spam e-mails. The computer-implemented method may additionally include identifying at least one additional spam e-mail sent via the mailing list. The computer-implemented method may also include transmitting information identifying the additional spam e-mail to at least one client on the mailing list. Various other methods, systems, and computer-readable media are also disclosed.