alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET DELETED Clod/Sereki Checkin Response"; flow:established,from_server; content:"|0d 0a 0d 0a|!chckOK!"; nocase; flowbits:isset,ET.clod1; reference:url,www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=Backdoor%3aWin32%2fSereki.A; reference:md5,bbb6ac2181dbbe15efd13c294cb991fa; reference:md5,3c39bfc78fcf3fe805c7472296bf6319; classtype:trojan-activity; sid:2010291; rev:5; metadata:created_at 2010_07_30, signature_severity Unknown, updated_at 2019_07_26;)