Thousands of known or suspected terrorists from across the globe were allowed to enter the U.S. unvetted under the Biden administration, a top counterterrorism official testified before a House committee hearing Thursday. Experts say the Trump administration should continue to tighten watchlist vetting and detention, as well as new immigrant vetting in order to correct the national security failures.

During a hearing before the House Homeland Security Committee, Director of the United States National Counterterrorism Center Joe Kent testified that up to 18,000 known or suspected terrorists (KSTs) from foreign countries have been identified by his agency so far, all of whom were allowed to enter the U.S. during the previous Biden administration’s open border policies.

“The No. 1 threat that we have right now, in my view, is the fact that we don’t know who came into our country in the last four years of Biden’s open borders,” Kent told the committee. He further added that the number of KSTs is likely higher due to the unknown number of individuals who crossed the border completely undetected during the Biden years.

The testimony came two weeks after an Afghan national named Rahmanullah Lakanwal ambushed two National Guardsmen in a targeted attack near the White House, killing one and seriously wounding the other. Lakanwal was admitted to the U.S. in 2021 as part of the Biden administration’s airlift of thousands of Afghans from the country in the midst of the chaotic withdrawal of U.S. military forces. Kent testified that 2,000 of the 18,000 KSTs arrived in America as a result of Biden’s Afghan airlift operations.

The vast number of reported KSTs contrasts starkly with the level of illegal immigration currently occurring under the Trump administration. Last week, the Department of Homeland Security reported that border encounters once again reached a record low for the month of November, with 30,367 total nationwide. The total number of enforcement encounters during the first 10 months of the Trump administration is “37% less than the monthly average of 185,625” during the Biden administration. In addition, the daily average of 245 apprehensions is “95% lower than the daily average under the last administration” of 5,110 per day. November also marked the seventh consecutive month in which the U.S. Border Patrol “released zero illegal aliens into the United States.”

Experts like Lt. Colonel (Ret.) Bob Maginnis, who serves as Family Research Council’s senior fellow for National Security, acknowledged that while the precise number of KSTs is disputed, the gravity of the situation cannot be ignored.

“There is a serious debate about the numbers, and we should deal in facts, not slogans,” he told The Washington Stand. “That specific figure of 18,000 is disputed by senior Biden-era officials, including former Homeland Security Secretary Alejandro Mayorkas, who has argued publicly that documented terrorist watchlist encounters number in the hundreds, not the tens of thousands. But focusing only on whether the number is 18,000 misses the larger and more disturbing reality.”

Maginnis continued, “Hundreds of individuals flagged on the federal terrorist watchlist were encountered at the border since 2021, according to congressional testimony — and some were released into the United States. At the same time, millions of migrants were allowed to enter or remain in the country under Biden’s policies, many from war-torn or failed states where reliable identity verification and intelligence vetting are extremely difficult. Common sense tells us that within a population that large, an unknown number of extremists, criminals, and terrorists of various stripes almost certainly slipped through.”

“That risk is no longer theoretical,” Maginnis went on. “The alleged shooter in the recent National Guard killing in Washington, D.C. reportedly entered the United States in the wake of President Biden’s disastrous withdrawal from Afghanistan. That chaotic evacuation rushed tens of thousands of people into the country under emergency conditions. Many were never fully vetted by traditional counterterrorism standards, and it is entirely plausible that dangerous individuals were among them. This case underscores what national security professionals warned at the time: speed replaced scrutiny, and the consequences are now emerging.”

As to what the Trump administration can do to address the situation, Maginnis listed five steps.

“The Trump administration must act decisively to correct these failures,” he argued. “First, it should order a full, declassified accounting of terrorist watchlist encounters, including how many individuals were released and under what authority. Second, it must restore a presumption of detention for anyone with a watchlist hit or unresolved identity concerns. Third, it should initiate continuous re-vetting of high-risk populations, particularly those admitted from conflict zones such as Afghanistan. Fourth, admissions from countries that cannot reliably verify identity should be paused or sharply restricted. Finally, the administration must close the border gaps that allow unscreened entries altogether and dismantle the smuggling networks that exploit them.”

Shortly after the D.C. National Guardsmen attack, the U.S. State Department announced that it had paused “visa issuance for individuals traveling on Afghan passports.”

“This is not about exaggerating numbers or demonizing immigrants,” Maginnis insisted. “It is about restoring a basic obligation of government: protecting the American people by enforcing borders, applying rigorous vetting, and putting national security first.”