Border guards stand by with machine guns to prevent Islamic militants from joining the flow, but within their sight smugglers offer to take travelers across for a surprisingly small fee. Abdul-Rauf, who gave only his first name for fear of prosecution for his illegal profession, said he could take clients within an hour and even help them carry their bags a few hundred meters (yards) into Syria. Abdul-Rauf, a thin man in his thirties with a close-cropped beard, asked whether the travelers were headed for territory controlled by pro-Western rebels or by the Islamic State group. Turkey, under pressure from its Western allies, stepped up its efforts to disrupt the flow of foreign fighters into Syria to join the Islamic State group, mainly with surveillance of travelers at airports and bus stations. "The measures that have been active right now will probably decrease all these activities, but bringing it to zero level — that is almost impossible," said Cemalettin Hasimi, an adviser to the Turkish prime minister's office. Aaron Stein, associate fellow at the Royal United Services Institute, a London-based think tank, said Turkey has done much to stop the flow of foreign fighters into the country: "They are tracking people to the best of their ability." The smugglers say a crackdown by authorities over the last year has made their work more dangerous, but the border remains porous because of their knowledge of its vulnerabilities and the complicity of some border guards, who can be bribed. Sipping tea in a black leather jacket, sandals and baseball cap in a cafe in Kilis, a smuggler who identified himself as Abu Mohammed said that he avoids foreign clients because undercover Turkish police officers have been leading a crackdown. Abu Mohammed said business has become more dangerous because border guards have stepped up their patrols and undercover work — but that the gap in the fence remains open and business continues because some of the border guard officers are corrupt.