Stocks in key security firms and weapons manufacturers have risen significantly since Friday night's terror attacks in Paris.
US defence industry stocks have hit record highs since the rise of ISIS, and the creation of the so-called Islamic State (IS).
Stocks in Lockheed Martin - one of the US military's main suppliers - rose by 3.5% when trading started on Monday.
Northrop Grumman, a global aerospace and defence technology company jumped by 4.4%, while American defence contractor Raytheon also enjoyed a 4% bounce.
Raytheon manufactures GPS-guided Tomahawk missiles which have been fired from ships at IS targets over 1,000 miles away. Monday saw it register its second-biggest one-day gain in the last three years.
The company previously had operations in Co. Derry - but left Northern Ireland in 2010.
Lockheed makes Hellfire missiles, they are currently being used by the US military in the Middle East.
Western Avionics' operation in Co. Clare is know to have designed software for the company.
Northrop Grumman recently won a contract to build a new stealth bomber for the US military worth $80bn (€75bn) - that's just under one third of Ireland's 2013 GDP.
AeroVironment - a drone firm used by the US also saw its stocks rise by 6%.
Frank Cilluffo, director of George Washington University's Centre for Cyber and Homeland Security discussed the market trend with CNN, saying, "You're going to see countries that hadn't seen spikes in spending from the past incidents increase spending."
While the events in Paris have inspired an escalation in air raids and political rhetoric - US President Barrack Obama has maintained that the US will not be putting fresh 'boots on the ground.'
"It is not just my view but the view of my closest military and civilian advisers that that would be a mistake," he said in the wake of the attacks.
This is not just a US phenomenon - key security stocks in the UK have also been on the rise.
Smiths Group, which makes detection systems for airports enjoyed a 10% surge - in spite of the fact that it reported a 4% fall in profits during its last quarter.
Rolls Royce it best know for its luxury cars - but it makes 15% of its revenues from the defence industry.
It has issued a series of profit warnings, and seen a major sell-off of its shares, but its stock rose by 5% when the markets re-opened on Monday.
David Cameron has committed to the UK's biggest increase in defence spending since the 7/7 bombings in 2005.
While France has pledged to fight IS - and refused to curb planned increases in military and security spending to meet EU fiscal rules.
