The recent arrest of eight Tajik nationals believed to have connections to ISIS has heightened concerns among national security officials that a dangerous affiliate of the now-splintered terror group could potentially carry out an attack on US soil, according to multiple US officials who spoke to CNN.

Members of the group initially entered the US at the southern border and requested asylum under US immigration law. It&rsquos unclear whether they entered at the same time and place.

By the time intelligence collected on overseas ISIS targets connected the men to the terror group, they had already been vetted by immigration authorities and allowed into the country, officials said.

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Though there is no hard evidence indicating they were sent to the US as part of a terror plot, at least some of the Tajik nationals had expressed extremist rhetoric in their communications, either on social media or in direct private communications that US intelligence was able to monitor, three officials said.

That discovery set off a flurry of emergency investigative efforts by federal agents and analysts across the country, sources said, including physical and electronic surveillance of the men &mdash a counterterrorism operation reminiscent of the years immediately following 9/11, when the FBI investigated numerous homegrown plots.

After a period of surveillance, federal officials in recent days faced a difficult decision: whether to continue surveilling the men in order to determine if they were part of any potential plot or wider terrorist network, or to move in and take them off the street. Rather than risk the worst-case scenario of a potential attack, senior US officials decided to move in and have the men apprehended by ICE agents, one source told CNN.

The men remain in federal custody on immigration charges and will eventually be deported following the counterterror investigation into them.

That discovery set off a flurry of emergency investigative efforts by federal agents and analysts across the country, sources said, including physical and electronic surveillance of the men &mdash a counterterrorism operation reminiscent of the years immediately following 9/11, when the FBI investigated numerous homegrown plots.／Flickr

Tajiks recruited by ISIS

Of particular concern to US officials was that the men hail from Tajikistan, a corner of Central Asia that in recent years has been a source of steady recruitment by ISIS-K, the Afghanistan-based affiliate of the Islamic terrorist group. ISIS-K is led primarily by Tajiks, who have carried out a series of recent attacks in Europe on behalf of the group, including the Crocus Hall attack in Moscow in March that killed more than 100 people.

National security officials fear that at least some of the eight Tajiks were ripe for radicalization by ISIS-K while they were inside the United States, potentially struggling with isolation, financial stress or discrimination &mdash all things that could make a person susceptible to ISIS propaganda glorifying violence.

Senior officials now see a so-called &ldquolone-wolf&rdquo attacker who emerges seemingly from nowhere as perhaps the more likely &mdash and potentially equally dangerous &mdash threat, rather than the more traditional coordinated plot carried out by trained operatives.

Compared to terror networks, whose communications can provide possible avenues for surveillance exploitation, lone individuals who do not telegraph their attack plans to anyone present an additionally difficult challenge for security officials.

&ldquoWe can&rsquot assume it&rsquos not all of the above,&rdquo said one senior US official. &ldquoWe&rsquore too early to know everything we want to know about the depth and texture of the links that might be there&rdquo between these eight people and ISIS.

The episode comes as senior intelligence officials have been publicly warning that global conditions have put the risk of a terror attack on US soil at its highest level in recent memory &mdash at the same time that many national security officials also acknowledge that American drawdowns in Afghanistan and elsewhere in the Middle East have reduced intelligence-gathering on traditional terrorism threats.

&ldquoIt&rsquos no secret that since our drawdowns in various places around the world, we collect less intelligence. This was always a tradeoff we knew we were making,&rdquo the senior US official said.

Former acting CIA Director Michael Morell this week co-wrote a widely circulated piece in Foreign Affairs warning that terrorism warning lights are &ldquoblinking red,&rdquo echoing a recent warning by FBI Director Christopher Wray, who said he sees &ldquoblinking lights everywhere I turn.&rdquo

&ldquoThe combination of stated intentions of terrorist groups, growing capabilities they have demonstrated in recent successful and failed attacks around the world, and the fact that several serious plots in the United States have been foiled, point us to an uncomfortable but unavoidable conclusion,&rdquo the Foreign Affairs piece read. &ldquoPut simply, the United States faces a serious threat of a terrorist attack in the months ahead.&rdquo

Gaps in intelligence collection

Intelligence officials are keenly aware of gaps in intelligence collection in Afghanistan, where ISIS-K is primarily based. While officials believe that ISIS-K mainly tries to radicalize and inspire attackers rather than train and field operatives, the group&rsquos rise to prominence is a relatively new phenomenon. That means that there is much that US counterterrorism analysts don&rsquot know about its strategy, recruitment efforts and operational tactics.

US officials and analysts who closely track Islamist terror groups do know that ISIS-K has dramatically ramped up its online propaganda machine. Rather than training and deploying fighters &mdash as al Qaeda did in the 9/11 attacks, for example &mdash ISIS-K has instead focused on radicalizing vulnerable populations. Tajikistan, for example, is one of the poorest countries in the world and its population faces extreme religious repression, both factors that terrorism experts say can make a population vulnerable to radicalization. 

Concerns about the border

The arrests also puts a spotlight on vulnerabilities at the US southern border, an issue Republicans have amplified in the midst of a presidential election year.

&ldquoWe are literally living on borrowed time,&rdquo Republican Oklahoma Sen. James Lankford said from the Senate floor on Wednesday during a speech about the threat of terrorists entering the US through the southern border.

A June 7 report released by the DHS inspector general found that asylum seekers were not always screened in a timely fashion and that border agents could not access all the federal data they needed to vet noncitizens seeking admission into the US.

The US is &ldquoat risk of admitting dangerous persons into the country or enabling asylum seekers who may pose significant threats to public safety and national security to continue to reside in the United States,&rdquo the report said.

US officials have been paying particular attention to immigrants from Central Asian countries including Tajikistan since last summer, when a group Uzbek nationals who had crossed the southern border were later found to have been assisted in traveling to the United States by a facilitator who had ties to ISIS.

The episode sparked a scramble across the US government to locate and investigate those people.

The arrests also puts a spotlight on vulnerabilities at the US southern border, an issue Republicans have amplified in the midst of a presidential election year.／Wikimedia Commons

Two US officials also said that it spurred national security officials to ensure that immigration and intelligence authorities were appropriately monitoring anyone traveling from Tajikistan, Uzbekistan and Kazakhstan.

&ldquoI think what [the incident with the Uzbek nationals] did last summer was suggest central Asians are potentially a population of concern, given what we know about the global ISIS network right now,&rdquo the senior US official said.

In 2023, CBP reported 169 encounters with individuals identified as &ldquopotential matches&rdquo with names on the terrorism watch list.

But that&rsquos not necessarily a reliable gauge of the number of actual terrorists who may be trying to enter the United States, US officials argue. When a name pings on a terror watch list, it could mean any number of things: a person could have a very loose, attenuated connection to a known terrorist. Or they could belong to a legacy terror group &mdash like the FARC &mdash that isn&rsquot known for conducting attacks on US soil. Or they could simply have a similar name as a person of legitimate concern.

That&rsquos what happened with the Jordanian national who was arrested at the gates of the US Marines base at Quantico earlier this year, two US officials said. Although his name returned a hit against one of the watch lists, it turned out to be a &ldquobad match,&rdquo according to the senior US official.

The blending of criminality and terrorism in poor countries &mdash like Tajikistan &mdash can also prove incredibly difficult for law enforcement officials to unravel. A person may have regular contact with a family member who has done some paid work for ISIS, for example, without themselves sharing any sympathy for the group.

But, Clarke said, the risk is there: &ldquoCrushing poverty [and] an extremely religious population that&rsquos suppressed by its leaders &mdash it&rsquos almost a perfect formula for exporting jihadists.&rdquo

Said one law enforcement source: &ldquoIt&rsquos become cliché, but remains absolutely true: We may be done with ISIS, but ISIS isn&rsquot done with us.&rdquo