若 SOAP 消息含有不會到期的時間戳，則它可能容易受到 replay 攻擊。
Nonce 是隨消息一起發送的加密隨機值，可防止 replay 攻擊。將 nonce 與時間戳（或有效期）結合使用時，每個消息都是唯一的，且只能在特定時間內有效，從而可以防止重新傳輸舊的消息。
[1] Standards Mapping - OWASP Top 10 2004 - (OWASP 2004) A10 Insecure Configuration Management
[2] Standards Mapping - OWASP Top 10 2010 - (OWASP 2010) A6 Security Misconfiguration
[3] Standards Mapping - FIPS200 - (FISMA) CM
[4] Standards Mapping - Common Weakness Enumeration - (CWE) CWE ID 254
[5] Standards Mapping - Web Application Security Consortium 24 + 2 - (WASC 24 + 2) Insufficient Authentication
[6] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 - (PCI 1.1) Requirement 6.5.10
[7] Web Services Handbook for WebSphere Application Server 6.1 IBM Redbooks
[8] Web Services Security Username Token Profile 1.0 OASIS