alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET WEB_SPECIFIC_APPS PHPStudy Remote Code Execution Backdoor"; flow:established,to_server; http.method; content:"GET"; http.header; content:"Accept-Charset|3a 20|"; fast_pattern; nocase; pcre:"/^(?:[A-Za-z0-9+/]{4})*(?:[A-Za-z0-9+/]{2}==|[A-Za-z0-9+/]{3}=|[A-Za-z0-9+/]{4})\x0d\x0a/R"; reference:url,www.cnblogs.com/-qing-/p/11575622.html; reference:url,www.uedbox.com/post/59265/; classtype:attempted-admin; sid:2028629; rev:1; metadata:affected_product Web_Server_Applications, attack_target Server, created_at 2019_09_25, deployment Perimeter, performance_impact Significant, signature_severity Major, updated_at 2019_09_25, mitre_tactic_id TA0001, mitre_tactic_name Initial_Access, mitre_technique_id T1190, mitre_technique_name Exploit_Public_Facing_Application;)