Detecting Active Attacks

OpenVAS is the ideal tool for detecting and shutting down vulnerabilities before they are exploited. But tools such as OpenVAS are of little help if an attack is already underway. To detect an ongoing attack, an intrusion detection system is the best option. The best-known IDS on the open source scene is probably Suricata, and there are now quite a few Suricata heuristics descriptions for attacks on IoT devices on the web.

You will want to combine the capabilities of Suricata and OpenVAS in a smart way. If OpenVAS fails as the first line of defense in your battle against attackers, at least Suricata will tell you about attacks currently taking place. There are many signs that can unmask such an attack, such as a sudden and unexpected increase in traffic. Certain types of network traffic are also good indicators of complex attacks.

The good news is that you can now use Suricata as an application in the form of a container on the Raspberry Pi. Jason Ish provides some containers [2] for this purpose; setting them up on the Raspberry Pi itself is basically just like setting up OpenVAS. Unlike OpenVAS, however, Suricata comes as a single container, so you don't need Docker Compose. However, it is not a good idea to run Suricata on the same RaspPi as OpenVAS. The resources the mini-computer offers are simply not up to the task. To use both services, you have to invest in two Raspberry Pis; in return, though, you can look forward to a far more secure setup within your own four walls.

Look online for a description of how to get Suricata up and running on a Raspberry Pi [3]. Although the instructions refer to a version of the service compiled locally from the source code, most of the details, such as the configuration settings, can also be transferred to the variant in a Docker container. Several sites on the web offer IoT heuristics for Suricata. These rulesets are what enable the application to detect IoT-based attacks in the first place (Figure 5). Some IoT parameters can also be found in the source code for the heuristics set that comes with Suricata.

Figure 5: Suricata does not detect existing vulnerabilities but uses heuristic observations to detect ongoing attacks. © Wikipedia / Linux Screenshots

For Suricata to meaningfully monitor traffic on its own network, the router needs to have a mirror feature, which means that it mirrors all traffic flowing through it on one port of the device, making it appear that all the traffic is flowing through that port. If your own router does not support this feature, you might have to try a manageable switch – manageable switches usually offer a mirror feature. The details depend heavily on the local setup.

Conclusions

Home users are not completely at the mercy of vendors when it comes to security. Powerful tools from the Linux world such as OpenVAS and Suricata help to nip attacks in the bud or at least detect them while they are in progress, giving you a chance to respond. The golden standards of Internet security also apply in the context of IoT devices. Regular updates to fix bugs, smart default configurations of devices such as routers, and sensible practices such as avoiding default credentials require very little effort but are highly effective. Users of IoT devices would do well to heed these rules – at the end of the day, that is the price you pay for the convenience of having IoT appliances.