alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE SEASALT Client Checkin"; flow:established,to_server; dsize:7; content:"fxftest"; depth:7; reference:md5,5e0df5b28a349d46ac8cc7d9e5e61a96; reference:url,www.mandiant.com/apt1; classtype:command-and-control; sid:2016441; rev:2; metadata:created_at 2013_02_20, signature_severity Major, updated_at 2019_07_26;)