00741nam a2200217Ia 4500 CTU_158113 210402s9999 xx 000 0 und d 38.10 004.69 P844 Porter, Thomas How to cheat at Voip security Thomas Porter, Michael Gough Rockland, MA Syngress 2007 The Perfect Reference for the Multitasked SysAdmin Internet telephony,Computer networks,Điện thoại internet,Mạng máy tính Security measures,Security measures,Mức độ an toàn,Mức độ an toàn Năm Trung tâm Học liệu Trường Đại học Cần Thơ