alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET MALWARE Known Sinkhole Response Header CERT.PL"; flow:established,from_server; http.content_len; byte_test:0,=,24,0,string,dec; file.data; content:"Sinkholed by CERT.PL"; within:24; fast_pattern; classtype:trojan-activity; sid:2020172; rev:4; metadata:created_at 2015_01_13, confidence High, signature_severity Minor, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_11_17;)