This paper provides an overview of the IEC 62645, an actual standard by the International Electrotechnical Commission (IEC) focused on the issue of requirements for computer security programs and system development processes to prevent and/or minimize the impact of cyber attacks against computer-based I&C systems. Developed since 2009 and published end of 2014, the standard is intended to be used for changing or establishing new security programs for I&C systems of operating and new Nuclear Power Plants (NPP). This paper also presents the key issues being considered in the new revision to IEC 62645, currently in process.