Assessing the Use of Insecure ICS Protocols via IXP Network Traffic Analysis

TL;DR

This study compares active scanning with large-scale traffic analysis at an IXP to assess the real use of insecure ICS protocols, revealing significant vulnerabilities and limited detection by traditional scanning methods.

Contribution

It introduces a large-scale IXP traffic analysis approach to accurately identify ICS communications and assess security practices, surpassing limitations of active scanning methods.

Findings

Shodan detects less than 2% of actual ICS hosts exchanging traffic.

Only 7% of Shodan-identified hosts actually exchange industrial traffic.

75.6% of ICS hosts use unencrypted, insecure communications.

Abstract

Modern Industrial Control Systems (ICSs) allow remote communication through the Internet using industrial protocols that were not designed to work with external networks. To understand security issues related to this practice, prior work usually relies on active scans by researchers or services such as Shodan. While such scans can identify publicly open ports, they cannot identify legitimate use of insecure industrial traffic. In particular, source-based filtering in Network Address Translation or Firewalls prevent detection by active scanning, but do not ensure that insecure communication is not manipulated in transit. In this work, we compare Shodan-only analysis with large-scale traffic analysis at a local Internet Exchange Point (IXP), based on sFlow sampling. This setup allows us to identify ICS endpoints actually exchanging industrial traffic over the Internet. Besides, we are able to detect scanning activities and what other type of traffic is exchanged by the systems (i.e., IT traffic). We find that Shodan only listed less than 2% of hosts that we identified as exchanging industrial traffic, and only 7% of hosts identified by Shodan actually exchange industrial traffic. Therefore, Shodan do not allow to understand the actual use of insecure industrial protocols on the Internet and the current security practices in ICS communications. We show that 75.6% of ICS hosts still rely on unencrypted communications without integrity protection, leaving those critical systems vulnerable to malicious attacks.