This paper provides a legal overview of the Russian secrecy regulations in one of the areas, namely communication secrecy, taken as a representative example to which big data technologies may be especially relevant if applied to analysis of masses of information that is sensitive, but at the same time very promising if processed by the big data instruments. The main legal challenge for processing of this information on a large scale is not only personal data laws, but also very special secrecy regimes of their kind. The authors analyze the applicable rules, heavily focus on detailed analysis of the voluminous case law, and provide argument for the directions of development of legislation that may enable more infusion of “open” big data technologies into these areas. The directions are focused around re-defining of legal concepts in this area, providing formal certainty of the definition of personal data and explicit recognition of anonymization techniques employing removal of “linking codes”. The authors use formal legal method and discuss the topic from the domestic legal perspective; hence, it may be useful, inter alia, for comparative legal research.