Since the inception of malware, the primary objective of its authors has been to either hide or camouflage their identities and locations in the Internet. To do this, attackers use traditional techniques based on the manipulation of TCP/IP elements as well as the most modern attack methods conceived to provide anonymity in the Internet. In this respect, the growing body of research into improving network anonymity intended to protect well-behaved users against malicious users has actually benefited the attackers. In this article, we describe the aforementioned techniques, i.e. those based on traditional concepts and those that apply recent mechanisms used by attackers in order to protect their identity. We also discuss the need to provide anonymity to Internet users without creating new vulnerabilities that open the door to dishonest intentions.