Donald Trump would have you believe that extremist jihadist refugees are flooding into the US without any oversight, saying that “hundreds of recent immigrants and their children have been convicted of terrorist activity inside the U.S.” Immigrants and their children (Donald Trump is one…) account for one quarter of the US population, and approximately 139 immigrants and 184 of their children have been implicated in jihadist activity in the US since 9/11. So he wasn’t completely wrong by saying “hundreds” were implicated, he just exaggerated the scope of nearly 100 million people.

Trump went on to assail the system set up to allow refugees in.

Under [Clinton’s] plan, we would admit hundreds of thousands of refugees from the most dangerous countries on Earth with no way to screen who they are, what they are, what they believe, where they come from.

This is simply untrue, and does a real disservice to the hardworking men and women that screen refugees every day in multiple security organizations around the world. As usual, Politifact covered this and did an excellent job of examining the process for a refugee to be admitted to the US:

The vetting begins with the United Nations High Commissioner for Refugee, which determines who counts as a refugee, who should be resettled (about 1 percent) and which countries would take them. This alone can take four to 10 months.

If the UNHCR refers refugees to the United States, they then face scrutiny from federal intelligence and security agencies.

Their names, biographical information and fingerprints are run through federal terrorism and criminal databases. Meanwhile, the refugees are interviewed by Department of Homeland Security officials. If approved, they then undergo a medical screening, a match with sponsor agencies, “cultural orientation” classes and one final security clearance.

Syrian refugees in particular must clear one additional hurdle. Their documents are placed under extra scrutiny and cross-referenced with classified and unclassified information.

The process typically takes one to two years or longer and happens before a refuge ever steps onto American soil. Ultimately, says the State Department, about half are approved, and there’s no real precedent of a terrorist slipping in through the vetting system.

This system has been in place for 30 years and was reevaluated after 9/11. It is not perfect and has come under criticism. Many refugees are coming from war torn areas where documents have been destroyed. Syrian refugees have more documents than many other refugee groups, but fake documents can be a problem. No system to vet immigrants will be perfect, but to say that there is no system in place is wrong, insults the intelligence of the American public and disparages these victims of war.

Sources:
http://www.npr.org/2016/06/22/483100251/fact-check-trumps-speech-on-clinton-annotated
http://www.politifact.com/truth-o-meter/article/2016/jun/22/fact-checking-donald-trumps-speech-about-hillary-c/
http://www.politifact.com/truth-o-meter/statements/2016/jun/13/donald-trump/wrong-donald-trump-says-theres-no-system-vet-refug/