Abstract Motivated by the study of security issues in molecular communication, this paper addresses the problem of secure communication in a bio‐inspired field where confidentiality of the information is of significant importance. The new metrics are used for the secrecy analysis where eavesdropper's decodability of confidential message and amount of information leakage is taken into account, which is not considered using conventional secrecy outage probability. A diffusion‐based molecular communication system is considered where the information to be transmitted is the time of release of the molecules. Typically in the existing literature in molecular timing channels, the position of the eavesdropper is known, which is usually an unpractical assumption. If no information about eavesdropper is known, it could be located at any distance with probability distribution be assumed to be uniform and Gaussian. In this paper, the closed‐form expressions for the eavesdropper capacity, generalised secrecy outage probability, average fractional equivocation and average information leakage rate have been obtained when the eavesdropper is located at a random distance from the transmitter.