1. A computer-implemented method for improving forest-based malware detection within an organization, at least a portion of the method being performed by a backend computing system comprising at least one processor, the method comprising: receiving, at the backend computing system, organization data from at least one organization computing device within an organization computer network; adjusting, at the backend computing system, a general use forest model to generate an organization-specific forest model for detecting malicious computer files within the organization computer network, wherein adjusting the general use forest model comprises changing a weight of at least one leaf node of the general use forest model based on the organization data; sending, from the backend computing system, the organization-specific forest model to the at least one organization computing device; detecting, by the backend computing system the at least one organization computing device, using the organization-specific forest model, malware in a file received on the at least one organization computing device within the organization computer network; and performing a security action with respect to the file to protect the backend computing system or the at least one organization computing device or both.