To protect your data, you must understand the traffic on your network. This task has become even more challenging with widespread use of the Transport Layer Security (TLS) protocol, which inhibits traditional network security monitoring techniques. The good news is that TLS fingerprinting can help you understand your traffic without interfering with any of the security benefits TLS brings to applications and complements current solutions like Encrypted Traffic Analytics [9]. To help our customers better understand the benefits of the approach, and to help drive the development and adoption of defensive uses of traffic analysis, the Advanced Security Research team of Cisco