U.S. Attorney General Eric Holder is worried about wholes that are greater than the sum of their parts . Take , for instance , the current mix of bomb-makers from Yemen with foreign fighters in Syria . `` That 's a deadly combination , where you have people who have the technical know-how along with the people who have this kind of fervor to give their lives in support of a cause that is directed at the United States and directed at its allies . And it 's something that gives us really extreme , extreme concern , '' he told ABC 's `` This Week . '' He estimated there are about 7,000 foreign fighters in Syria , coming from places like Europe and the United States . `` In some ways , it 's more frightening than anything I think I 've seen as attorney general , '' he said . `` This is a situation that we can see developing and the potential that I see coming up , the negative potential I see coming out of the facts in Syria and Iraq now , are quite concerning , '' he said . Since it started in 2011 , the conflict in Syria has left more than 150,00 dead and some 680,000 injured . Then there 's the humanitarian crisis for the survivors , with the United Nations estimating that more than 9.3 million need help and that at least 6.5 million have been forced from their homes into other parts of Syria . Another 2.5 million are now refugees in neighboring countries . And threats from that part of the world are n't the only ones Holder has to worry about . He also fears potential attacks on planes . This month , the Transportation Security Administration said that security screeners at overseas airports may ask U.S.-bound passengers to turn on their electronic devices to prove they work and are n't explosive devices . They wo n't allow devices without power on board planes . The traveler may then undergo additional screening . It 's part of an update to security measures aimed at combating potential new threats from terrorists in the Middle East and Europe . `` This is not a test ... We 're doing something in reaction to things that we have detected , '' Holder told ABC about the upgrades . `` We are at a dangerous time , '' he said . U.S. attorney general urges new laws to prevent terror from returning fighters .
Holder is concerned about a mix of bomb-makers and foreign fighters . The U.S. attorney general talks to ABC 's `` This Week '' Recent security upgrades are `` not a test , '' he says .