alert http $EXTERNAL_NET any -> $HTTP_SERVERS any (msg:"ET EXPLOIT Possible WebShell GIF Upload"; flow:established,to_server; http.method; content:"POST"; http.request_body; content:"GIF89a"; depth:6; content:"<%eval|20|request|28 22|"; distance:0; fast_pattern; classtype:attempted-admin; sid:2027736; rev:2; metadata:attack_target Web_Server, created_at 2019_07_22, deployment Perimeter, performance_impact Low, confidence Medium, signature_severity Major, tag WebShell, updated_at 2020_08_31;)