1. A method for determining a safety level of a network vulnerable to attack from at least one origin to at least one target, the network comprising at least one machine having at least one component, comprising: associating, with a computer, at least one machine with at least one component; associating, with the computer, the at least one component with at least one of a plurality of vulnerabilities; determining, with the computer, a plurality of degrees of similarity among the plurality of vulnerabilities; grouping, with the computer, subsets of the plurality of vulnerabilities based on their determined degrees of similarity to one another, wherein each group of vulnerabilities is subject to a distinct zero day exploit; generating, with the computer, an attack graph describing exploitation of the plurality of vulnerabilities, the attack graph defining exploit condition relationships between at least one origin and at least one target; analyzing, with the computer, the attack graph using a k-zero day metric function; and determining, with the computer, a safety level based on the analysis of the attack graph using the k-zero day metric function.