Abstract. Although privacy is often seen as an essential right for internet users, the provision of anonymity can also provide the ultimate cover for malicious users. Privacy Enhancing Technologies (PETs) should not only hide the identity of legitimate users but also provide means by which evidence of malicious activity can be gathered. This paper proposes a forensic investigation technique, which can be embedded in the framework of existing PETs , thereby adding network forensic functionality to the PET. This approach introduces a new dimension to the implementation of Privacy Enhancing Technologies, which enhances their viability in the global network environment.