(CNN) President-elect Joe Biden's approach to Russia is now an even tougher challenge with news that Moscow may be responsible for a massive cyber attack on US federal agencies -- one Biden said he will impose "costs" for. The President-elect and his team are preparing a "cost imposition strategy" to respond to Russia -- not just for the hack, if Moscow is responsible, but for Russia's other disruptive actions also -- measures that will include but won't be limited to sanctions, according to a source close to Biden.