All 12 defendants are members of the GRU, a Russian federation intelligence agency within the main intelligence directorate of the Russian military, who were acting in "their official capacities".
A dozen Russian intelligence officers are facing new USA federal indictments alleging they hacked into American computers with the explicit intention of interfering with the 2016 presidential election.
A federal grand jury on Friday indicted the Russian intelligence officers on charges of hacking the computer networks of 2016 Democratic presidential candidate Hillary Clinton and the Democratic Party, he said.
Along with breaking into the DNC and Clinton's campaign, the spies named in the indictment also hacked the state boards of elections, secretaries of state and companies that provided election software to steal information about voters.
The attacks were a signature feature of Russia's active measures against the United States; embarrassing emails were passed to Wikileaks, which released them publicly. It claims that they created fictitious online personas, including "DCLeaks" and "Guccifer 2.0", and used them to release the documents starting un June 2016.
Friday's indictments come ahead of Tuesday's scheduled meeting between President Trump and Russian President Vladimir Putin.
In just over a year since his appointment as special counsel, Robert Mueller and his hand-picked team of prosecutors have filed nine indictments covering twenty individuals and three businesses, earned five guilty pleas, have two criminal cases headed to trial, and sentenced one person to prison.
"It's important not to think as Republicans or Democrats, but patriotically as Americans", he said.
Mr Rosenstein said the defendants corresponded with several Americans during the alleged conspiracy, but added there is no allegation that any USA citizen committed a crime. On Feb. 16, his prosecutors charged 13 Russians and three Russian entities they said were part of a broader effort to sow discord among USA voters through social media - which they used to impersonate Americans, coordinate with unwitting US activists and even plan rallies.