alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET DELETED Clod/Sereki Checkin with C&C (noalert)"; flow:established,to_server; content:"GET"; nocase; http_method; content:"/chck.dat"; fast_pattern; http_uri; content:!"User-Agent|3a|"; http_header; content:!"Referer|3a|"; http_header; flowbits:set,ET.clod1; flowbits:noalert; 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:2010290; rev:11; metadata:created_at 2010_07_30, signature_severity Unknown, updated_at 2019_07_26;)