alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"ET MALWARE Mac Flashback Checkin 2"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/scheck/"; http.user_agent; pcre:"/^[A-Za-z0-9+\/=]+?$/"; classtype:command-and-control; sid:2014598; rev:7; metadata:created_at 2012_04_17, signature_severity Major, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2020_04_22;)