FLIR Systems' Ocean Scout camera. Image: FLIR Systems.

Investors came into Monday's trading session thinking that the market could drop substantially in response to Friday night's terrorist attacks in Paris. Yet stocks quickly moved upward once the market opened Monday morning, and FLIR Systems (NASDAQ:FLIR), PRA Group (NASDAQ:PRAA), and Baytex Energy (NYSE:BTE) were among the best performers on the day.

FLIR Systems jumped more than 10% as investors sought to ramp up their exposure to defense-related stocks. With the terrorist threat on the rise, many believe that governments around the world will be more willing to spend on sophisticated technology to help fight against potential attacks. FLIR's emphasis on thermal imaging and other sophisticated detection and surveillance equipment could put it in an especially strong position in fighting against terrorists, especially if it can demonstrate its ability to recognize individual threats in time to prevent future attacks. FLIR's latest earnings report showed some challenges, but some believe that the company has potential to respond favorably to this latest opportunity.

PRA Group rose 11% as the debt-collection specialist tried to recover from its recent earnings-related drop. Earlier this month, PRA Group stock fell almost 40% as it reported falling revenue and much worse declines in net income than most investors had expected. The company has also had to deal with fallout from a September settlement with the Consumer Financial Protection Bureau, which involved PRA Group paying penalties of $8 million and refunding $19 million to consumers. Yet in an investor presentation the company released through an SEC filing, PRA Group remains excited about its ability to grow regardless of macroeconomic conditions. The debt collector sees the change to grow its market share around the world, with barriers to entry preventing competition in the U.S. and PRA Group's international focus potentially paying off in the long run.

Finally, Baytex Energy soared 17% on a strong day for the energy complex. Oil prices rose after threatening to break below the $40 per barrel level, which many feared would have led to further declines that could have sent oil prices to their lowest levels since 2009. As a small independent oil and gas producer, Baytex has gotten hit especially hard, and it has had to suspend its heavy-oil drilling in Canada and slowed its pace of development in the Eagle Ford. Investors clearly hope that Baytex will see still-higher prices in the near future, but with the company having suspended its dividend, Baytex will need further improvement before it has a chance of returning to its former growth trajectory.

The son of PRA Group's CEO is currently employed by The Motley Fool. Dan Caplinger has no position in any stocks mentioned. The Motley Fool owns shares of and recommends PRA Group. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.