The BitTorrent protocol is transparent; it exposes a user's IP address to the swarm. Older clients may contain unpatched vulnerabilities that could theoretically be exploited by malicious actors within the swarm or by copyright enforcement agencies. Furthermore, using an outdated client on a modern operating system can lead to compatibility issues. The irony of the situation is that users seeking "cleaner" software (legacy versions) are exposing themselves to "dirty" vulnerabilities inherent in unmaintained code.