alert tls $EXTERNAL_NET any -> $HOME_NET any (
msg:"ET INFO Possible JARM Fingerprinting Client Hello via tls1_3_middle_out";
flow:established,to_client;
content:"|16 03 01|"; startswith;
content:"|c0 12 c0 13 c0 07 c0 27 cc 14 c0 2f 13 01 c0 14 13 02 c0 28 cc a9 c0 30 c0 73 c0 60 c0 72 c0 61 c0 2c c0 76 c0 af c0 77 c0 ad cc a8 c0 24 13 05 c0 0a 13 04 c0 2b 13 03 c0 ae cc 13 c0 ac c0 11 c0 23 00 0a c0 09 00 2f c0 08 00 3c 00 9a c0 9c 00 c4 c0 a0 00 88 00 9c 00 be 00 35 00 45 00 3d 00 9f c0 9d c0 a3 c0 a1 c0 9f 00 9d 00 6b 00 41 00 39 00 ba 00 9e 00 84 c0 a2 00 c0 c0 9e 00 07 00 67 00 04 00 33 00 05 00 16|"; fast_pattern;
content:"|02|hq|03|h2c|02|h2|06|spdy/3|06|spdy/2|06|spdy/1|08|http/1.1|08|http/1.0|08|http/0.9";
content:"|03 04 03 03 03 02 03 01|"; endswith;
reference:url,engineering.salesforce.com/easily-identify-malicious-servers-on-the-internet-with-jarm-e095edac525a;
classtype:misc-activity;
sid:2036700; rev:1;
metadata:affected_product Windows_XP_Vista_7_8_10_Server_32_64_Bit, attack_target Client_Endpoint, created_at 2022_05_25, deployment Perimeter, deployment SSLDecrypt, confidence High, signature_severity Informational, tag Description_Generated_By_Proofpoint_Nexus, updated_at 2022_05_25;
)