A source told the Herald: "Just because he is up North does not mean that Duffy thinks that his many enemies in Dublin cannot go after him.
"He rarely leaves his home and is so worried that he has set up a number of cameras at the house in case someone tries to attack it."
'Whacker' Duffy (40) had been living in Dublin since his release from prison in March of last year, but he had to endure "credible threats" from other dissident Republicans as well as associates of a major Crumlin/Drimnagh-based gang.
Originally from Armagh, Duffy joined the Irish National Liberation Army (INLA) in the 1980s.
He was still a teenager when he was involved in the murder of Sergeant Michael Newman in Derby, England, in 1992.
It was not until July 2010 that he was convicted and received a life sentence for this murder of the unarmed police officer, who was shot once through the side of the head at point-blank range as he reached his car.
However, Duffy was released from jail earlier last year under the terms of the Good Friday Agreement.
Before being convicted of that murder, Duffy had served jail time here for membership of the INLA as well as his role in the infamous Ballymount Bloodbath.
In 1999 his group took six men from a rival gang hostage and beat and tortured them in Ballymount industrial estate.
During a bitter fight, INLA man Patrick Campbell was killed by machete blows.
Duffy served nine years in prison for false imprisonment and possession of a gun.
He was released in 2007 but immediately became involved in a bitter gangland feud with dangerous criminals based in the south inner city, Crumlin and Tallaght areas of the capital before being arrested and convicted of membership of an illegal organisation in 2008.
Before Duffy fled back to his Northern bolthole, he had been spotted with slain mobster Stephen 'Dougie' Moran, who was shot dead at his Lucan home in March.
At a previous court hearing, Duffy said he had renounced his paramilitary past and wanted to make a fresh start with his family back in the North.
"I'm finished with violence and just want to have a normal life. I'm moving back to Armagh," he said at the Special Criminal Court in 2009.