"Researchers at Akamai have been monitoring the growth of attacks leveraging Internet of Things (IoT) devices. These attacks are coming from compromised devices of various sorts. Akamai works hard to protect our customers and users from these attacks.
With other, non-IoT types of devices (including general purpose computers), owners can patch or reconfigure their systems to close vulnerabilities. In the Internet of Things, device owners are often at the mercy of vendor updates in order to remove their devices from the pool of botnet nodes. In some cases, IoT devices are entirely unpatchable and will remain vulnerable until removed from service."
Or, you can read the SSHowdown paper here.