( CNN ) -- For a while , it seemed that the threat from ISIS was limited to sparsely populated desert regions in the Middle East . Through brutal tactics and persecution of minorities , the Sunni extremist group brought slaughter and chaos to large areas of Syria and Iraq . But its merciless efforts to establish its version of an Islamic caliphate unsettled the wider region , prompting U.S. airstrikes aimed at stemming its advance . The Islamic militant group has responded by beheading three of its Western hostages in recent weeks , ratcheting up the crisis . It has also amped up the rhetoric , threatening attacks on the United States and its allies . On Monday , several countries quickly rejected the threats , which were made in an audio recording from an ISIS leader who urged attacks on civilians in the United States and other Western nations . The situation underscores the question of what ISIS hopes to gain through the intensifying conflict with the United States and its allies . What has ISIS been saying about the U.S. ? ISIS , which calls itself the `` Islamic State , '' has been ramping up its threats against the United States and the West for months . The extremist group publicly warned of `` direct confrontation '' with the U.S. as far back as January , according to the National Counterterrorism Center . ISIS has also `` repeatedly taunted Americans , '' the center said , notably during the recent videotaped executions of journalists James Foley and Steven Sotloff . The killings of Foley and Sotloff took place after the U.S. military began airstrikes against ISIS positions in Iraq to help Kurdish and Iraqi forces beat back the militants ' rapid advance . President Obama has since announced his anti-ISIS strategy , which is expected to involve expanding the airstrikes into the chaotic Syrian battle zone . The U.S. has also been working to build up a coalition of countries to help counter the threat from ISIS , which is also known as ISIL . Why is ISIS so eager to pick a fight with America ? This summer , ISIS declared the establishment of a `` caliphate , '' an Islamic state stretching across the territory it has conquered . A former ISIS fighter told CNN this month that the group 's main aim is `` to establish an Islamic state that will encompass the Arab world . '' `` And after that , we go to other countries , '' the man said in an interview in Turkey . With that goal in mind , taunting and antagonizing the world 's foremost military power may not seem like the wisest way for ISIS leader Abu Bakr al-Baghdadi to expand and consolidate his territory in the Middle East . But analysts say that for the group to be seen around the world as locked in battle with the U.S. is an effective means of rallying more fighters to ISIS ' banner . `` For al-Baghdadi , fighting America and its coalition of 40 countries is a badge of honor , a powerful recruiting tool . It is proof that he and his organization have become the leaders of global jihad , toppling al Qaeda , their rival in that contest , '' world affairs columnist Frida Ghitis wrote in a commentary for CNN . Will it work ? With the U.S. military carrying out strikes against ISIS forces , the extremist group is able to exploit the situation for propaganda purposes . The group said the executions of Foley and Sotloff were in response to the American airstrikes in Iraq . `` I 'm back , Obama , and I 'm back because of your arrogant foreign policy towards the Islamic State , '' the executioner says in the video of Sotloff 's beheading . `` Just as your missiles continue to strike our people , our knife will continue to strike the necks of your people . '' The beheadings further intensified attention on ISIS and its efforts to impose its heavy-handed rule on parts of Iraq and Syria . U.S. intelligence officials estimate that more than 2,000 Europeans and more than 100 Americans have flocked Syria to fight with extremist groups there . They say it 's unclear precisely how many of them have joined ISIS . But the strategy could backfire . `` ISIS is gambling that drawing America and the West into the fight will make it stronger , but if the West is strategic and smart , this move will prove to be ISIS ' worst mistake , '' said Ghitis . What kind of threat does ISIS pose to the U.S. ? U.S. officials say that ISIS fighters are n't a direct threat to the U.S. homeland at the moment . `` At this point , we have no information that ISIL is plotting an attack inside the United States , '' Matthew Olsen , the director of the National Counterterrorism Center , said last week in testimony to Congress . The dangers , officials say , are to U.S. personnel and infrastructure in Iraq -- and from militants with U.S. or other Western passports potentially returning home and staging attacks . `` What really worries American counterterrorism officials is that ISIS will prioritize launching attacks against the United States , will train Western recruits in bomb-making and send them back , '' said CNN terrorism analyst Paul Cruickshank . The suspect in the deadly shooting at Belgium 's Jewish Museum in May recently spent a year in Syria and is a radicalized Islamist , according to French officials . Prosecutors say that when police arrested the French citizen , they also seized a Kalashnikov rifle wrapped in a flag bearing the ISIS insignia . What about the risk of homegrown attacks ? That 's what security analysts say is cause for concern -- and what ISIS appears to be urging in its new audio message . Attacks by homegrown terrorists are n't new . In recent years , the United States has experienced the horror of the Boston Marathon bombings and the Fort Hood shooting . Al Qaeda has long urged individuals in the West to mount their own attacks , providing instructions on matters like bomb-making in its magazine , Inspire . The Boston marathon bombers used pressure cooker devices they apparently learned to make online . The National Counterterrorism Center says homegrown violent extremists are `` the most likely immediate threat to the homeland . '' It estimates that the level of activity of such extremists has remained consistent over the past few years , but that ISIS ' influence could start to play a role . `` We remain mindful of the possibility that an ISIL-sympathizer could conduct a limited , self-directed attack here at home with no warning , '' the center says . Officials say they are particularly concerned about ISIS ' skillful use of propaganda , particularly on social media , to reach an audience in the West . Have there already been any cases of ISIS-inspired attackers in the West ? U.S. authorities have alleged that a man who owns an upstate New York food store funded ISIS , tried to send jihadists to Syria and plotted to kill U.S. troops who had served in Iraq . Mufid A. Elfgeeh , 30 , was arrested on May 31 , though federal officials did n't outline the case against him until last week . Elfgeeh , a naturalized U.S. citizen from Yemen , has pleaded not guilty to the charges , which include trying `` to provide material support to a foreign terrorist organization '' and attempting to kill officers and employees of the United States . In Australia , whose government has pledged combat aircraft and military advisers to the fight against ISIS , authorities carried out a large-scale anti-terrorism operation last week . Australian Prime Minister Tony Abbott said that an Australian high up in ISIS had been calling on his networks in Australia to carry out `` demonstration killings . '' Australian media reported that the alleged assailants planned to kidnap a member of the public , behead the victim and then drape him or her in an ISIS flag . Authorities declined to give details about the threat , citing an ongoing operation . Was the U.S. slow to grasp the scale of the ISIS menace ? While ISIS has been taunting the United States for months -- including publishing images of American soldiers engulfed in flames in its online magazine -- some critics have suggested Obama initially underestimated the extremist group . In particular , the President 's comments to The New Yorker in January have been singled out . `` The analogy we use around here sometimes , and I think is accurate , is if a J.V . team puts on Lakers uniforms , that does n't make them Kobe Bryant , '' Obama told the magazine . Months later , Obama ordered airstrikes against the group , which he has described as a `` cancer . '' His defense secretary , Chuck Hagel , said last month the threat from ISIS was `` beyond anything we have seen . '' But senior administration officials have defended Obama 's earlier characterization of the extremists . `` The President was right , '' Deputy National Security Adviser Tony Blinken told CNN last month . `` They did not pose a threat like al Qaeda central to us in the homeland . ''
Fighting the U.S. is ` ` a code of conduct '' that helps ISIS recruitment , he said . But taking on the world 's top military leader also comes with risks . American intelligence officials have said they 're not aware of an ISIS presence inside the U.S .