With less than a week to go before the Fourth of July holiday weekend, many experts are concerned about a possible terror attack.

On Friday, the Department of Homeland Security issued a memo warning of a potential terror threat for Independence Day. "We are encouraging all law enforcement to be vigilant and prepared. We will also adjust security measures, seen and unseen as necessary to project the American People," the memo said.

The warning comes after three attacks in France, Tunisia, and the Middle East, which have killed dozens. Additionally, on Monday, a second New Jersey resident in a month was arrested and charged with conspiring to join the Islamic State terror group overseas.

Peter Caram, a retired Port Authority police officer and Islamic terrorism expert, believes the threats against the United States are real.

"New Jersey is not alone," Carman says. "These individuals have been recruited usually through social media or the Internet, so we are not unique in that respect...As long as these individuals feel emboldened and we feel we have weakened security posture, they can strike at any time."

Caram says that anyone who sees something suspicious should report it, as it is often the best defense authorities have when tracking down anyone suspected of terror.

The expert does say that despite the warnings, Americans should not have to alter their plans on any given day. 

The Department of Homeland Security did not mention any specific threat or a specific target in the warning.