Large botnets made up of Internet-of-Things (IoT) devices have a steady presence in the threat landscape since 2016. However, it has not explained how attackers maintain control over their botnets. In this paper, we present a long-term analysis of the infrastructure of IoT botnets based on 36 months of data gathered via honeypots and the monitoring of botnet infrastructure. We collected 64,260 IoT malware samples, 35,494 download servers, and 4,736 C&C servers during 2016 to 2021. Not only are most binaries distributed for less than three days, but the connection of bots to the rest of the botnet is also short-lived. To reach the C&C server, the binaries typically contain only a single hard-coded IP address or domain. Long-term dynamic analysis finds no mechanism for the attackers to migrate the bots to a new C&C server. Although malware binaries that use domain names to connect to their C&C servers increased in 2020, the C&C servers themselves have a short lifespan and this tendency has not changed. The picture that emerges is that of highly disposable botnets. IoT botnets are reconstituted from scratch all the time rather than maintained.@en

Geographically distributed infrastructures, such as buildings, dams, and solar power plants, are commonly maintained via Internet-connected remote management devices. Previous studies on detecting and securing industrial control systems (ICS) have overlooked these remote management devices, as they do not expose ICS-specific services like Modbus and BACnet and thus do not show up in Internet-wide scans for such services. In this paper, we implement and validate a discovery method for these devices via their Web User Interface (WebUI) and detect 890 devices in Japan alone. We also show that many of these devices are highly insecure. Many allow access to the status or even the control over industrial systems without proper authentication. Taking a closer look at three prevalent remote management devices, we discovered 13 0-day vulnerabilities, several of which were rated as medium or high severity. They have been responsibly disclosed to the manufacturers. By using honeypots that imitate these systems, we show that over time, only a small number of attackers enter these systems, but some do change critical parameters. Attackers appear to interact more with the system when more facility information is displayed on the WebUI. Finally, we notified operators of 317 vulnerable remote management devices by email and telephone. We reached 212 persons in charge of the devices and received confirmation that our method had correctly identified the device. 50% of the persons in charge of the devices stated that they mitigated or will mitigate the problem. We confirmed their actions via a followup scan for vulnerable devices and found that measures were taken for 58% of the devices when we could reach the persons in charge of the device.@en

Large botnets made up of Internet-of-Things (IoT) devices have been a steady presence in the threat landscape since 2016. Earlier research has found preliminary evidence that the IoT binaries and C&C infrastructure were only seen for very brief periods. It has not explained how attackers maintain control over their botnets. We present a more comprehensive analysis of the infrastructure of IoT botnets based on 23 months of data gathered via honeypots and the monitoring of botnet infrastructure. We collected 59,884 IoT malware samples, 35,494 download servers, and 2,747 C&C servers. We focuse on three dominant families: Bashlite, Mirai, and Tsunami. The picture that emerges is that of highly disposable botnets. IoT botnet are not so much maintained as reconstituted from scratch all the time. Not only are most binaries distributed for less than three days, the connection of bots to the rest of the botnet is also short-lived. To reach the C&C server, the binaries typically contain only a single hard-coded IP address or domain. The C&C servers themselves also have a short lifespan. Long-term dynamic analysis finds no mechanism for the attackers to migrate the bots to a new C&C server. In other words, bots are used only immediately after capture and then abandoned - -perhaps to be recaptured again via the aggressive scanning practices that these botnets are known for. While IoT botnets appear less advanced than Windows-based botnets, the advantage of being disposable means that they are very resistant to blacklisting and C&C takedown. Most IP addresses are used only once and never seen again. The question that arises is how attackers source these addresses. We speculate that they might be abusing the IP address allocation practices of cloud providers.@en