Methods and systems are provided for a proactive approach for computer forensic investigations. The invention allows organizations anticipating the need for forensic analysis to prepare in advance. Digital signatures are generated proactively for a specified target. The digital signature represents a digest of the content of the target, and can be readily stored. Searching and comparing digital signatures allows quick and accurate identification of targets having identical or similar content. Computational and storage costs are expended in advance, which allow more efficient computer forensic investigations. The present invention can be applied to numerous applications, such as computer forensic evidence gathering, misuse detection, network intrusion detection, and unauthorized network traffic detection and prevention.