Though the BB84 protocol has provable security over a noiseless quantum channel, the security is not proven over current noisy technology. The level of tolerable error on such systems is still unclear, as is how much information about a raw key may be obtained by an eavesdropper. We develop a reproducible test to determine the security–or lack thereof–of the protocol in practice. This enables us to obtain an experimental estimate of the information that can be obtained using asymmetric phase-covariant cloning to eavesdrop on the BB84 protocol.