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MIAMI (CBSMiami) – President-elect Donald Trump has returned to New York after spending the holidays at his Mar-a-Lago Resort in Palm Beach.

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Mr. Trump will be briefed this week by intelligence officials on links between Russia and cyber attacks aimed at interfering with the U.S. election. During his annual New Year’s Eve bash, the President-elect said he’s still not convinced that Russia was responsible and he alluded to having insider information that he would share in the next few days.

Well, I just want them to be sure because it’s a pretty serious charge,” said Trump. “Hacking is a very hard thing to prove. So it could be somebody else. I also know things that no one else knows.”

Congressman Adam Schiff, the top Democrat on the House Intelligence Committee, expressed his disbelief. On a weekend talk show he said all of the members of the intelligence committees in Congress, both Democrats and Republicans, have no question that the Russians were involved. He added that the only one who does question their involvement is Trump.

Over the weekend, President Barack Obama ordered his team to modernize technology at the White House, including new computers and faster internet. But the upgrade may not win over Mr. Trump who say no computer is safe.

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“It’s very important, if you have something really important, write it out and have it delivered by courier, the old fashioned way,” said Trump.

Early Monday Morning, 35 Russian diplomats and their family members ordered out by the Obama administration returned to Russia.

Sean Spicer, Mr. Trump’s incoming White House Press Secretary, suggested the move may have been unfair.

“I mean you look at 35 people being expelled, two sites being closed down, the question is, is that response in proportion to the actions taken,” questioned Spicer.

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Republican John McCain has scheduled a Senate hearing on Russian hacking for this Thursday. Members of Congress on both sides have vowed to hit Russia in the pocketbook– with broader economic sanctions.