The head of MI5 has said most dissident republican attacks in Northern Ireland were prevented last year.
Andrew Parker disclosed there were more than 20 carried out and for every one police have foiled three or four others.
The director general of the security service said the armed groups continued to target police, prison officers and others.
At a speech in London, he said: “Northern Ireland experience teaches us that terrorist threats are enduring; that it requires sustained long-term effort and teamwork to counter them; and that it’s unrealistic to expect every attack plan to be stopped, even where the perpetrators may in some cases have been on our radar for many years.
“Whilst there has been great progress in Northern Ireland, dissident republicans continue to carry out terrorist attacks aimed at the police, prison officers and others.
“There were more than 20 such attacks in 2014, most of which - thankfully - were unsuccessful.
“The key statistic is that for every one of those attacks we and our colleagues in the police have stopped three or four others coming to fruition.”
DUP Upper Bann MP David Simpson said Mr Parker’s comments represented a sobering reminder of the threat posed.
“We cannot reduce our guard against those who would drag Northern Ireland back to the past.”
He said dissidents’ links to organised crime were well known.
“As such it is vital that the National Crime Agency (NCA) should operate fully here. These terrorist gangs must be tackled from every angle, and by cutting their source of funds it helps cut them off at the roots.
“It would also ensure that vital resources are freed up within the local policing budget to assist with other priorities.”
Nationalists in Northern Ireland have blocked the full operation of the NCA in Northern Ireland over accountability concerns.