alert tls $EXTERNAL_NET any -> $HOME_NET any (msg:"SUSPICIOUS [PTsecurity] Dropbox SSL Payload Request pkt checker #0"; flow:established, to_client; content:"|1603 01|"; depth:3; content:"www.dropbox.com0"; distance:0; within:2044; fast_pattern; stream_size:server, <,2045; stream_size:client, >,0; stream_size:server, >,0; stream_size:client, <,300; flowbits:noalert; flowbits:set, FB309001_0; threshold:type limit, track by_src, count 1, seconds 30; classtype:misc-activity; metadata:created_at 2017_8_8; reference:url, github.com/ptresearch/AttackDetection; sid:11001732; rev:1;)