It starts with a tweet . The recruit has been slowly and carefully chosen from his local community -- perhaps at a mosque , or gym , or cafe -- by an al Qaeda recruiter , aiming to send a Westerner to fight alongside radicals in Syria . According to a defector from the ranks of the Islamic State in Iraq and Syria ( ISIS ) -- whose stronghold in the Syrian town of Raqqa punishes smokers and insists women wear a veil -- the jihadist group runs a series of internet welcome chat groups to begin the process of indoctrinating and filtering potential recruits from outside Syria . The defector agreed to an interview with CNN but wanted to hide his identity , but his story was ratified by a witness and his extensive knowledge of life inside Syria under the ISIS . He fled Syria when two of his relatives were killed in the violence , and is now hiding in Turkey . He said that European recruits were more sought after and treated in a different class by the recruiters . `` There was special treatment for the Europeans , '' he says . `` One British guy said he was called Ibrahim , then told me he was from Manchester . One asked my emir [ his unit 's head ] if he should fight in his own country , or come to Syria . He was told if God does n't give you martyrdom in Syria , then he could wage war in his own country . '' Western officials have told CNN they are deeply concerned at not only the growing numbers of Western passport holders who have traveled to Syria to fight , but also the potential for more and more of these radicals to return to the West and continue that jihad through acts of domestic terrorism . Hundreds of British and French citizens have traveled to Syria , according to multiple official estimates , and several have returned . A Briton was recently convicted of terror offenses after spending time inside Syria with radical groups . U.S. officials have become increasingly concerned about American passport holders attempting the same , and anxieties have been amplified by the U.S. State Department confirming that Moner Mohammad Abu-Salha , from Florida , became the first American citizen to die as a suicide bomber in Syria last month . Recruiters are the gateway from the West to ISIS . The first contact is made over Twitter , when the recruit might send a message to ISIS 's Twitter accounts saying `` Can I talk to Hakim , '' for example , the source said . The Twitter account is then followed back , enabling a direct message to be sent with the e-mail address of the ISIS recruiter . The conversations that continue , the defector said , over Google Chat , Skype and Twitter , are extensively monitored by the emirs and supervisors of the recruiting unit . While the defector did n't speak English , he says he used online translating apps to talk to French and English recruits . `` There are questions I am allowed to answer , '' he said , `` and then things I must ask my supervisor . Specific questions about religion . I have to get their permission to message anyone . I ca n't talk on Skype , as everything is written down , so they can monitor everything . '' The defector added his supervisor often dealt with the European recruits . He said the online chats , intended to provide basic information about life under the ISIS caliphate , or strict Islamist state , lasted about two weeks , and sometimes each chat could last hours . He said some of the potential recruits asked curious questions . `` I remember one guy asked me for a video of a public execution '' , he said , `` but one that 's not been put online before . Strange ones too about marrying Syrians girls . I got mad once when I was asked if someone could marry three or four girls . '' When the recruit is ready to come to Syria , a different part of ISIS assists , and the defector said he was not supposed to meet those he helped recruit . He said the recruitment was first aimed at filling ISIS ranks inside Syria , and that the return of these radicals to their home countries was carefully regulated by the emirs , or senior commanders , of ISIS . Each recruit 's passport was taken from him on arrival and the defector recalls seeing dozens of foreign passports held in the same office , and overhearing one foreign recruit discussing how he might return home to act as a recruiter . The defector was himself jailed for one day by ISIS for overstepping the permitted topics of conversation with recruits , and says he fled Syria with the clothes on his back after his relatives were killed . He says he still fears for his life and has given his phone number to only three people . `` I did n't think ISIS lied to me , '' he says , `` but they did play with my mind . ''
Islamist defector says Twitter , Google Chat and Skype used to recruit foreign fighters . West is concerned foreign fighters may return to their countries with terrorist plots . Defector says foreign fighters are recruited over weeks . He says one group wanted to make an online video ; he asked about it .