Mirai Botnet Creates Army of IoT Orcs

This post was based on analysis by Yashashree Gund and RaviKant Tiwari.

There is a lot of speculation in the news about surveillance from home appliances, personal electronics, or other Internet of Things (IoT) devices. Although some statements may be hyperbole, we know that these devices, in homes and offices, are being compromised and used to attack others.

On October 21, 2016, the first major cyberattack using IoT devices as weapons was a massive flood of network traffic aimed at Dyn, a company that operates domain name and traffic optimization services. Peak traffic was measured at 1.2Tbps, the highest ever recorded for this type of attack. Analysis revealed that the attack came from a large number of webcams, compromised by Mirai botnet malware.

Mirai infects most IoT devices by scanning for open Telnet or SSH ports, and then using a short dictionary of common default usernames and passwords to break into vulnerable devices. After gaining entry, the malware drops a small binary program on the device, which fetches the full Mirai bot executable. Each infected bot searches for other vulnerable IoT devices, rapidly expanding the botnet. A network scan conducted by McAfee in late 2016 identified 40,000 infected IoT devices active and online, about 2.5 million infected devices that were offline, and about five devices newly infected every minute.

During the infection phase, the control server monitors the infection process until it “owns” enough IoT devices for whatever campaign the attacker has planned. When the attacker decides to initiate an attack, commands are sent to the bots to select the attack type and target. Mirai is capable of executing almost a dozen attack types at different layers, making it difficult to intercept. When the attacker determines that countermeasures are reducing the effectiveness of one attack type, Mirai can quickly switch to another type, working at the network, transport, or application layers.

Before the October attack on Dyn, the Mirai source code was released, and several Mirai-based botnets began offering attacks-as-a-service, using up to 100,000 bots, for less than $0.08 per bot. Since the source code release, additional Mirai variants have surfaced, as other cybercriminals look to build on the success of this malware family. We expect a steady release of new variants, targeting different devices, attack types, antidefense measures, and evasion techniques. The source code and attack-as-a-service offerings have made Mirai available to a wide range of individuals, greatly expanding the list of potential victims.

To test Mirai’s attack methods and infection speed, we set up a “honeypot,” simulating a vulnerable IoT device. (Watch our video.) Within a minute, we registered the first attempt to log in with default credentials.

We also monitored Mirai attack activity during a two-day period and counted 34 attacks by multiple Mirai botnets, mostly against targets in the United States, but also some in Germany, the Netherlands, and the United Kingdom. Targets were mostly gaming servers, as well as a few individuals, web shops, a dating site, and even another attack site. This would appear to confirm that even amateur attackers can use Mirai for their own ends.

The best defense against Mirai attacks on IoT devices is to change default passwords and usernames, and to use strong and unique passwords across all devices. The list of passwords used by Mirai to compromise IoT devices is disturbingly short and basic, including variations of “12345,” “admin,” “password,” “default,” and the name of the manufacturer. To bolster defenses, keep IoT device software up to date, segment IoT devices from other parts of the network, disable unused device services and ports, and periodically power-cycle IoT devices.

For more information on Mirai and best practices for securing your network and IoT devices, download the McAfee Labs Threats Report: April 2017.

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