  HTTPS is quickly rising alongside the need of Internet users to benefit from
security and privacy when accessing the Web, and it becomes the predominant
application protocol on the Internet. This migration towards a secure Web using
HTTPS comes with important challenges related to the management of HTTPS
traffic to guarantee basic network properties such as security, QoS,
reliability, etc. But encryption undermines the effectiveness of standard
monitoring techniques and makes it difficult for ISPs and network
administrators to properly identify and manage the services behind HTTPS
traffic. This survey details the techniques used to monitor HTTPS traffic, from
the most basic level of protocol identification (TLS, HTTPS), to the finest
identification of precise services. We show that protocol identification is
well mastered while more precise levels keep being challenging despite recent
advances. We also describe practical solutions that lead us to discuss the
trade-off between security and privacy and the research directions to guarantee
both of them.
