引言
SQL注入是一种常见的网络攻击手段，攻击者通过在数据库查询中注入恶意SQL代码，从而获取、修改或删除数据库中的数据。本文将以DVWA（Damn Vulnerable Web Application）这个专门用于安全学习和测试的Web应用程序为例，深入探讨Medium难度下的SQL注入攻击技巧和案例分析。
DVWA简介
DVWA是一个开源的PHP/MySQL Web应用程序，它旨在帮助安全专家和安全爱好者学习和测试Web应用程序的安全性。DVWA提供了多种安全级别，从低到高，分别对应不同的安全防护措施。
Medium难度SQL注入概述
在Medium难度下，DVWA对SQL注入的防护措施有所增强，但仍存在漏洞。以下是一些常见的攻击技巧：
1. 基本注入技巧
- 联合查询（Union Query）：通过构造联合查询，攻击者可以尝试从数据库中获取额外的数据。 “`sql ‘ OR 1=1 UNION SELECT NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, 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