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Before the start of business, Just Security provides a curated summary of up-to-the-minute developments at home and abroad. Here’s today’s news.

TRUMP-RUSSIA

The Russian disinformation campaign around the 2016 presidential election used every significant social media platform to further the prospects of then-candidate Donald Trump’s presidential bid — and worked even harder to support Trump while in office – according to a report prepared for the Senate by Oxford University’s Computational Propaganda Project and network analysis firm Graphika. The report is reportedly the first to study the millions of posts provided by major technology firms to the Senate Intelligence Committee; the bipartisan panel has not yet announced whether it endorses the report’s findings but is planning to release it publicly along with another study later this week, Craig Timberg and Tony Romm report at the Washington Post.

The office of special counsel Robert Mueller rejected on Friday a suggestion from former Trump national security adviser Michael Flynn that he had been tricked into lying to F.B.I. agents investigating Russia’s election interference and ties to Trump associates. Following Flynn’s lawyers’ request for lenient sentencing last week, Mueller’s prosecutors submitted court papers arguing that “a sitting national security adviser, former head of an intelligence agency, retired lieutenant general and 33-year veteran of the armed forces knows he should not lie to federal agents … he does not need to be warned it is a crime to lie to federal agents to know the importance of telling them the truth,” Adam Goldman reports at the New York Times.

The Mueller probe has reportedly cost the Department of Justice (D.O.J) more than $25 million, according to new and previous expenditure reports. Lydia Wheeler reports at the Hill.

Mueller is allegedly embroiled in a closed-door legal battle. Following Friday’s confidential hearing in the case at the federal courthouse in Washington, Michael S. Schmidt provides an explainer on what is known of the secret dispute at the New York Times.

Trump’s former personal lawyer Michael Cohen – facing jail time after pleading guilty to a raft of offences – said in an interview Friday that he knew arranging hush money payments during the 2016 campaign on Trump’s behalf was wrong. “I am angry at myself because I knew what I was doing was wrong,” Cohen said, adding “of course” when asked by the ABC News anchor George Stephanopoulos whether the president was fully aware of what he was doing when Cohen made the payments, Maggie Haberman and Eileen Sullivan report at the New York Times.

Trump’s current personal lawyer Rudy Giuliani claimed yesterday that he could “produce 20 witnesses” to testify that hush money payments were intended to protect then-candidate Trump’s family — rather than to influence the outcome of the presidential race. “I can produce an enormous number of witnesses,” Giuliani told Stephanopoulos during an interview on “This Week,” adding: “I can produce 20 witnesses to tell you what he was concerned about,” Quint Forgey reports at POLITICO.

Giuliani appeared to slightly shift the timeline about how long discussions went on in 2016 about a potential Trump Tower project in Moscow. Giulinani said yesterday that “according to the answer that [Cohen] gave, it would have covered all the way up to November of – covered all the way up to November 2016 … the President didn’t hide this;” when asked about the difference between that comment and the previous claim that Trump’s discussions about the project ended in January 2016, Giuliani responded, “until you actually sit down and answer the questions and you go back and you look at the papers and you look at … you’re not going to know what happened,” Eli Watkins and Dana Bash report at CNN.

The U.S. fears for the safety of Mariia Butina, who pleaded guilty on Thursday to being an unregistered agent of Russia in the U.S., according to court filings made by prosecutors that were briefly made public Friday. “Although the fact of defendant Butina’s cooperation is now public, the details of her transportation to and from the jail are not,” Justice Department lawyers told U.S. District Judge Tanya Chutkan, John Bowden reports at the Hill.

“What will the special counsel … do if he finds evidence that the president is implicated in crimes having to do with Russian interference in the election?” A short explainer on whether it might be possible for a sitting president to be indicted while in office is provided at the Economist.

Far from winding down – the Mueller probe has taken on a renewed energy in recent weeks, Jack Shafer comments at POLITICO Magazine, arguing “I think I’m on safe ground to predict that the Trump inquiries have many, many more innings to go.”

IMMIGRATION

Senior adviser to the White House Stephen Miller insisted yesterday that the administration is prepared to shut down the government in order to get the funding it demands to build its long-promised wall on the U.S.-Mexico border, stating: “we’re going to do whatever is necessary to build the border wall.” Democrats “flatly refused” to give ground in order to help avoid the threatened government freeze, the Guardian reports.

Attorneys for the father of Guatemalan girl Jakelin Caal Maqui – who died a week ago in Border Patrol custody – said Saturday that her family is asking the U.S. government for a “neutral and transparent” investigation into her death. Alicia A. Caldwell reports at the Wall Street Journal.

The TRUMP ADMINISTRATION

President Trump on Friday named his budget chief Mick Mulvaney as acting White House chief of staff, in a move to end speculation that he was having a difficult time finding a new occupant for the role. “For the record, there were MANY people who wanted to be the White House Chief of Staff,” Trump said in a message on Twitter, adding “Mick M will do a GREAT job!” Jessica Taylor reports at NPR.

A video has emerged showing Mulvaney calling the president a “terrible person.” The footage – taken at a debate shortly before the presidential election in 2016 – shows Mulvaney stating: “yes, I am supporting Donald Trump, but I’m doing so despite the fact that I think he’s a terrible human being” The BBC reports.

An analysis of the many obstacles facing acting attorney general Mark Whittaker and the strategy he may adopt to navigate them, is provided at Reuters.

YEMEN

An “immediate ceasefire” in the Yemeni war will come into effect tomorrow, according to officials, after the initial agreed ceasefire deal was threatened by a fresh bout of violence. The government-in-exile and the Iran-aligned Shi’ite Houthi rebels agreed to end fighting in the vital port city of Hodeidah last Thursday, but on Friday air strikes and fierce clashes were reported between the sides, the BBC reports.

A U.N. monitoring unit is expected to arrive in the region within days to ensure that the terms of the deal are carried out, with the group led by Dutch Maj. Gen. Patrick Cammaert – a veteran of former U.N. peacekeeping missions in Congo and in Ethiopia and Eritrea. “Being present in the field soon is an essential part of the confidence that needs to go with the implementation of this agreement,” U.N. Special Envoy Martin Griffiths told members of the U.N. Security Council at a special meeting Friday, adding that a robust monitoring system was “urgently needed,” Farnaz Fassihi reports at the Wall Street Journal.

“After two and a half years of missed opportunities … I think it’s fair to say that the political process to find a comprehensive solution to the conflict in Yemen has finally resumed,” Griffiths commented following last week’s peace talks in the rural Swedish town of Rimbo. “This is no small achievement, made possible first and foremost by the commitment of the parties and the credit goes to them … I was extremely impressed by their dedication … all made concessions, all engaged in depth and at length, intensively and in good faith,” Al Jazeera reports.

JAMAL KHASHOGGI KILLING

Saudi Arabia issued an “unusually strong” rebuke of the U.S. Senate early today, rejecting a bipartisan resolution that leveled blame on Saudi crown prince Mohammed bin Salman for the killing of Washington Post columnist Jamal Khashoggi. In a lengthy statement, Saudi Arabia stated that the Senate’s resolution “contained blatant interferences” in the kingdom’s internal affairs and was based on “unsubstantiated claims and allegations,” adding: “the kingdom categorically rejects any interference in its internal affairs, any and all accusations, in any manner, that disrespect its leadership … and any attempts to undermine its sovereignty or diminish its stature,” the AP reports.

Turkish President  Recep Tayyip Erdogan said on Friday that the perpetrators in Khashoggi’s murder were “well known” and that audio recordings of the killing illustrate that people close to bin Salman  were involved. Making the comments at the Organisation of Islamic Cooperation’s (O.I.C.) judicial conference in Istanbul, Erdogan claimed that the instructions given to the individuals responsible were handled “professionally,” Al Jazeera reports.

“Trump’s unquestioning support for Mohammed bin Salman is putting at risk broader U.S. interests in the Middle East,”– even if the Trump administration is hesitating to tell the “whole truth” about the Khashoggi case rather than outright lying. Brian P. McKeon comments at Foreign Policy.

SYRIA

A bomb blast in a northwestern Syrian town held by Turkish-backed opposition forces killed at least eight people and wounded two dozen yesterday, according to activists and local security. The AP reports.

Turkey would consider working with Syrian President Bashar al-Assad if he were to win a democratic election, Turkish Foreign Minister Mevlut Cavusoglu told a conference in Qatar yesterday. Reuters reports.

U.S.-led airstrikes continue. U.S. and coalition forces carried out 251 airstrikes against Islamic State targets in Syria between Dec 2. and Dec. 8. [Central Command]

OTHER DEVELOPMENTS

The Israeli Defense Force (I.D.F.) yesterday claimed to have found a fourth cross-border tunnel allegedly dug by Iran-backed Lebanese militant group Hezbollah along the Israel-Lebanon frontier. In a statement, the I.D.F. said the tunnel was “under the army’s control and does not pose a threat anymore … the tunnel was blown up just as what happened to the previous tunnels, and anyone who enters it from Lebanese territory would be in danger.” Al Jazeera reports.

Afghan Taliban representatives and U.S. officials are due to meet in the United Arab Emirates (U.A.E.) today, the militants’ main spokesperson announced, amid diplomatic attempts to establish the groundwork for talks that would end the 17-year conflict in Afghanistan. Reuters reports.

North Korea has condemned the U.S. over its latest round of sanctions, cautioning that Washington’s approach could “block the path to denuclearization on the Korean peninsula forever.” The latest development comes in the context of stalling nuclear talks, following the landmark Singapore summit between North Korean leader Kim Jong-un and President Trump in June, AFP reports.

“Geopolitical and economic rivalry between China and the U.S.– not a breach of Trump’s Iran sanctions – is what’s really behind [Huawei C.F.O.] Meng Wanzhou’s arrest,” Simon Tisdal comments at the Guardian, in an analysis of escalating “global rivalry” between Washington and Beijing.