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Here are five things you must know for Friday, Aug. 18:

1. -- A terror attack in Spain kept gains in U.S. stock futures to a minimum on Friday, Aug. 18. 

The S&P 500 and Dow Jones Industrial Average were little changed, while the Nasdaq made small moves higher. 

A stock selloff on Thursday, Aug. 17, sent benchmark indexes lower. A disappointing quarterly performance from Cisco Systems Inc. (CSCO)  triggered losses in the tech sector and led to a triple-digit decline on the Dow Jones Industrial Average. 

All Dow components ended in the red on Thursday, while the benchmark index suffered its worst daily performance since May. 

2. -- A terrorist attack in Spain set European markets on edge on Friday. 

Police shot dead five suspected terrorists, hours after a van slammed into a crowd in Barcelona on Thursday afternoon. Police killed the five would-be attackers in Cambrils, south of Barcelona, who had been planning a separate related attack, according to Reuters. The planned attack involved explosive belts, though those have now been determined to be fake. 

On Thursday, a van ran into a crowd along the tourist-heavy Las Ramblas avenue. That attack killed 13 people and injuring more than 100 others. ISIS claimed credit for the incident. 

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