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"We were curious if we could build a botnet out of freely available cloud services," said Rob Ragan, senior security associate for Bishop Fox, who has been experimenting on that premise for the past several years with his colleague Oscar Salazar, security associate at Bishop Fox. "We started getting all these emails and alerts of, 'Here's a free Amazon EC2 box, there's free storage space, here's a free platform to develop and host your code.' We thought, 'Wow! That is a lot of computing power for free.'"
The question they asked themselves was how hard would it be to automate the process of signing up for an unlimited number of free accounts from these sites and then developing a central control system from which an attacker could potentially launch malicious activities. The answer: not hard at all.
"We were really easily able to get hundreds of boxes on certain providers and have a central way to launch things like massive port scans," Ragan says. "We also did a proof-of-concept on cryptocurrency or Bitcoin mining. If you're getting this free computing power and don't have the power bill from it, why not use that to generate mining? That would be a huge motivation for malicious threat actors using these platforms." The project was made possible through the development of a process to automate the creation of unique email accounts on free email services, and then special scripting to automate the process of clicking on email verification links sent to those accounts.
The researchers initially refined that process during a penetration test of a sweepstakes website in which they showed an attacker could game the drawing and up the chances of winning through exactly such a method.
The process of developing the botnet came with the usual kinks. For example, the researchers told an amusing story about scrambling in the middle of the night to code a "stop" mechanism to their automated system once they turned it on and saw it worked.
"We had basically just coded the start button, and then we thought, 'Uh, oh! How do we stop it?'" Salazar said. "We had to quickly figure out how to stop our botnet from getting away from us."
Much of the abuse the pair tested was made possible due to poor verification of users during the trial account creation process. Even when some services tried to limit accounts by limiting Internet access, the researchers were easily able to employ quick workarounds. Of the 150 different PaaS and IaaS sites the duo tested, two-thirds were not doing any CAPTCHAs, SMS verification, or credit card verification beyond simple email account verification.
According to Ragan, while these extra steps can also be worked around, cloud services still need to embrace them in order to make it more expensive for potential attackers to do exactly what they did. Not only is it a huge vulnerability for these service providers, but it is opening them up to huge bills from Amazon because, in many instances, these services are launching free Amazon EC2 boxes on behalf of trial accounts. That is computing power they service providers will have to pay for in these abuse cases.
This is likely how attackers will try to work the system given that Amazon has implemented strict authentication controls to prevent exactly such kinds of abuse. "You could just register accounts. It didn't require SMS, it didn't require credit cards -- you just needed a valid email address, and then you'd have access to free Amazon EC2 boxes," Salazar said. "Over the last couple of years, Amazon has really increased its security, and now it requires a credit card and SMS and email verification. So Amazon is putting a bunch of protection around its services, and now these other companies starting up are basically leasing EC2 boxes, but they're not putting the same protections in place. So you're basically getting free Amazon boxes through them on their dime."
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