A method of processing communication in a computer network, comprising: accessing information related to requests from a plurality of clients for a plurality of domains, the information including: for each client, a set of domains associated with requests from the client, and for each domain, a set of clients associated with requests for the domain, the plurality of domains including a first set of known domains having a classification and a second set of unknown domains having no classification; iteratively generating (210, 214) security rankings for the plurality of clients, wherein the security ranking for each client is determined from the set of domains associated with the client by aggregating a security ranking of each domain associated with said client, based on the classification for the first set of the plurality of domains; iteratively generating (212, 214) security rankings for the plurality of domains, based on the security ranking for the plurality of clients, wherein the security ranking for each domain is based on the security rankings of the set of clients associated with requests for said domain by aggregating the security ranking of each client associated with said domain, wherein the security ranking for each client is based on a reciprocal determination from the security rankings of the set of domains associated with said client, wherein the security ranking for each domain is based on a reciprocal determination for the security rankings of the set of clients associated with said domain, wherein iteratively generating the security rankings for the plurality of clients at a current iteration is based on the security rankings for the plurality of domains from a previous iteration of iteratively generating (212, 214) the security rankings for the plurality of domains, and wherein iteratively generating the security rankings for the plurality of domains at a current iteration is based on the client security rankings from the previous iteration of iteratively generating (210, 214) the security rankings for the plurality of clients; and generating a domain classification for each domain of the second set of the plurality of domains, based on the security rankings of the second set of the plurality of domains. accessing information related to requests from a plurality of clients for a plurality of domains, the information including: for each client, a set of domains associated with requests from the client, and for each domain, a set of clients associated with requests for the domain, the plurality of domains including a first set of known domains having a classification and a second set of unknown domains having no classification; for each client, a set of domains associated with requests from the client, and for each domain, a set of clients associated with requests for the domain, the plurality of domains including a first set of known domains having a classification and a second set of unknown domains having no classification; iteratively generating (210, 214) security rankings for the plurality of clients, wherein the security ranking for each client is determined from the set of domains associated with the client by aggregating a security ranking of each domain associated with said client, based on the classification for the first set of the plurality of domains; iteratively generating (212, 214) security rankings for the plurality of domains, based on the security ranking for the plurality of clients, wherein the security ranking for each domain is based on the security rankings of the set of clients associated with requests for said domain by aggregating the security ranking of each client associated with said domain, wherein the security ranking for each client is based on a reciprocal determination from the security rankings of the set of domains associated with said client, wherein the security ranking for each domain is based on a reciprocal determination for the security rankings of the set of clients associated with said domain, wherein iteratively generating the security rankings for the plurality of clients at a current iteration is based on the security rankings for the plurality of domains from a previous iteration of iteratively generating (212, 214) the security rankings for the plurality of domains, and wherein iteratively generating the security rankings for the plurality of domains at a current iteration is based on the client security rankings from the previous iteration of iteratively generating (210, 214) the security rankings for the plurality of clients; and generating a domain classification for each domain of the second set of the plurality of domains, based on the security rankings of the second set of the plurality of domains.