说明：   基于IP网络及其协议的公共性质，使得VoIP天生就具备相对于传统电话网而言更易受到攻击的特质。不过，通过采取一个仔细规划的、多层次的VoIP网络防护措施，企业就可以让VoIP网络的安全程度赶上甚至是超过传统的电话系统
(IP-based network and its public nature of the agreement, making VoIP inherently possess relative to the traditional phone network more vulnerable in terms of character. However, by adopting a carefully planned, multi-level VoIP network protection measures, companies can make VoIP network security level to catch up with even more than the traditional phone system)