SYSTEM AND METHOD FOR RESTRICTING PATHWAYS TO HARMFUL HOSTS IN COMPUTER NETWORKS

System and method for detecting malicious activity in a computer network that includes hosts and connectors between the hosts. Network pathways to a plurality of investigated hosts are explored. A graph is formed based on results of the exploring of the network pathways. The graph represents topology of explored portions of the computer network, including connectors (e.g., communication links) between the investigated hosts and intermediary hosts situated along explored pathways that include the investigated hosts, and an indication of a prevalence of connectors in pathways to each of the investigated hosts. The prevalence of connectors along pathways to each of the investigated hosts is compared against a threshold, and any suspicious host situated along pathways to a common investigated host that is associated with a connector having a low prevalence that is below the prevalence threshold is identified. An access restriction can be associated with the suspicious host.