Encrypted Traffic Inference: An Alternative to Enterprise Network Traffic Decryption

Enterprises cannot afford to ignore the threat posed by encrypted inbound network traffic. Adversaries now commonly use encrypted traffic flows to cloak cyberattacks, slipping malware, ransomware, and other malicious content past perimeter detection systems.

But as many network security practitioners understand, finding and stopping encrypted threats requires gaining visibility into encrypted flows; that, in turn, requires decrypting and inspecting encrypted traffic, which is no easy task.

Decryption equipment is expensive to purchase and deploy, plus complex to configure and manage. Even in an ideal deployment scenario, backhauling traffic between remote users and a data center network security stack is increasingly untenable.

There may be a better way. What if it were possible to determine with near certainty whether an inbound encrypted network flow contained malcode without actually using decryption?

In newly published research from Omdia, Fundamentals of Network Traffic Decryption and Risk Management (Omdia subscription required, learn more here), we examine the state of both established and developing technologies for addressing the risk associated with inbound encrypted network traffic.

Some of our key findings include:

Fortunately, new techniques are emerging for addressing encrypted traffic risk. Some involved decryption in the cloud with an identity-aware proxy (IAP), while another called session key forwarding obtains encryption key pairs from host memory without the processor-intensive processes of proxying sessions, obtaining keys, and re-encrypting sessions. Both offer notable promise as alternatives to traditional decryption methods.

However, encrypted traffic inference (ETI) is perhaps the most fascinating of all emerging alternative approaches. ETI solutions analyze aspects of encrypted traffic flows to discern whether they are likely to be malicious, without using decryption.

Based on concepts first published by Cisco Systems researchers in 2016, ETI works by capturing encrypted network flow data attributes -- including DNS metadata, TLS handshake metadata, and HTTP packet headers – and analyzing them for specific, intricate patterns that indicate malicious activity.

A number of vendors – including Cisco, Juniper, NTA vendor Corelight, NDR provider IronNet, and specialist vendor Barac – all offer some degree of ETI capability today.

While ETI is promising, it remains nascent. Enterprises are only beginning to adopt the technology, so its ability to identify malicious traffic in encrypted flows consistently over a long period of time, while delivering consistent ROI, has yet to be determined. 

Still, enterprises should not ignore the significant potential ETI presents. Omdia believes that the most appropriate long-term encrypted traffic risk management solution for enterprises will likely combine ETI with decryption.

For example, an organization may use an ETI solution to provide a "first pass" on inbound encrypted flows. Most traffic would likely be deemed safe, but the presumably small percentage of flows found to be suspicious or inconclusive would then be decrypted for deep-packet inspection. This combination approach would decrease the need for decryption, lowering decryption-related costs, and allow for more flexible deployments across increasingly hybrid infrastructures.

Omdia recommends enterprises prioritize a review of their business strategy and technical approach to network traffic decryption and risk management, with an eye toward considering how ETI and other emerging capabilities have the potential to reduce cost and operational complexity while ensuring inbound encrypted flows are not a cybersecurity blind spot.

Related Content: