TLS in the Wild: An Internet-Wide Analysis of TLS-Based Protocols for Electronic Communication

TitleTLS in the Wild: An Internet-Wide Analysis of TLS-Based Protocols for Electronic Communication
Publication TypeConference Paper
Year of Publication2016
AuthorsHoltz, R., Amann J., Mehani O., Wachs M., & Kaafar M. Ali
Published inProceedings of the Network and Distributed System Security Symposium (NDSS)
Other Numbers3828

Email and chat still constitute the majority ofelectronic communication on the Internet. The standardisationand acceptance of protocols such as SMTP, IMAP, POP3, XMPP,and IRC has allowed to deploy servers for email and chat in adecentralised and interoperable fashion. These protocols can besecured by providing encryption with TLS—directly or via theSTARTTLS extension. X.509 PKIs and ad hoc methods can beleveraged to authenticate communication peers. However, secureconfiguration is not straight-forward and many combinationsof encryption and authentication mechanisms lead to insecuredeployments and potentially compromise of data in transit. Inthis paper, we present the largest study to date that investigatesthe security of our email and chat infrastructures. We used activeInternet-wide scans to determine the amount of secure servicedeployments, and employed passive monitoring to investigate towhich degree user agents actually choose secure mechanismsfor their communication. We addressed both client-to-serverinteractions as well as server-to-server forwarding. Apart from theauthentication and encryption mechanisms that the investigatedprotocols offer on the transport layer, we also investigated themethods for client authentication in use on the application layer.Our findings shed light on an insofar unexplored area of theInternet. Our results, in a nutshell, are a mix of both positiveand negative findings. While large providers offer good securityfor their users, most of our communication is poorly secured intransit, with weaknesses in the cryptographic setup and especiallyin the choice of authentication mechanisms. We present a list ofactionable changes to improve the situation.


This work was partially supported by funding provided to ICSI through National Science Foundation grants CNS : 1528156 (“Understanding the State of TLS Using Large-scale Passive Measurements”) and ACI : 1348077 ("A Bro Center of Expertise for the NSF Community"). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors or originators and do not necessarily reflect the views of the National Science Foundation.

Bibliographic Notes

Proceedings of the Network and Distributed System Security Symposium (NDSS), San Diego

Abbreviated Authors

R. Holtz, J. Amann, O. Mehani, M. Wachs, and M. A. Kaafar

ICSI Research Group

Networking and Security

ICSI Publication Type

Article in conference proceedings