ET WEB_CLIENT Generic Webshell Accessed on External Compromised Server

alert http $EXTERNAL_NET any -> $HOME_NET any (
    msg:"ET WEB_CLIENT Generic Webshell Accessed on External Compromised Server";
    flow:established,to_client;
    file.data;
    content:"<font><font>file Manager</font></font>"; nocase; distance:0;
    content:"<font><font>Back Connect"; nocase; distance:0;
    content:"<font><font>CgiShell</font></font>"; nocase; distance:0;
    content:"<font><font>Symlink</font></font>"; nocase; distance:0;
    content:"Mailer</font></font>"; nocase; distance:0;
    content:"<font><font>Auto r00t</font></font>"; nocase; distance:0;
    content:"<font><font>Upload</font></font>"; nocase; distance:0;
    content:"Exploiter & scan Tools</font></font>"; nocase; distance:0; fast_pattern;
    content:"<font><font>Self remove</font></font>"; nocase; distance:0;
    classtype:web-application-attack;
    sid:2029916; rev:2;
    metadata:affected_product Web_Server_Applications, attack_target Web_Server, created_at 2020_04_15, deployment Perimeter, confidence Medium, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_04_15;
)