November 3, 2016 By Douglas Bonderud 2 min read

Malicious actors have historically passed over programmable logic controllers (PLCs) — the devices that control and monitor sensors, valves and motors in the manufacturing and energy industries — in favor of easier targets. Until recently, PLCs were separated from public-facing networks.

Thanks to the rise of Internet of Things (IoT) deployments, companies have started to shift away from internal-only models. As noted by CSO Online, however, this also opened the door for security researchers to create a new kind of PLC malware that leverages existing problems with microprocessors to operate undetected and wreak significant havoc.

Pin Pals

It’s important to note that this malware isn’t out in the wild and won’t be anytime soon, according to developer Ali Abbasi, who will present his findings at the upcoming Black Hat Europe 2016 conference. Instead, his work is designed to highlight the next generation of potential issues and encourage manufacturers to correct existing PLC problems before sending new iterations to market.

So what’s the problem? It all starts with pins. PLCs use specific configurations of input/output (I/O) pins to both monitor and control the status of specific hardware, sensors or tools. These embedded computers are found everywhere, from power stations and factories to public utility companies and gas refineries. Abbasi’s new PLC malware is able to switch the I/O configuration of PLC pins to fundamentally change the way the computer operates.

Consider the case of a valve controlled and monitored by a PLC. Via output commands, the controller can tell the valve to open or close. Through input, it receives pressure readings. By switching the pins, attackers could prevent the valve from operating and send false monitoring data. Even worse, since there are no hardware interrupts for any systems on a chip (SoC) pin configurations, the PLC logic controller won’t report any errors when the pins are switched.

To outside observers, the system appears to be working as intended, but it is in fact fully compromised. While original iterations of the PLC malware required root access, researchers were also able to design alternatives that leveraged the PLC runtime to reconfigure the pins via memory corruption. While easier ways to compromise PLCs currently exist, Abbasi’s discovery points to the bigger problem of completely obfuscated attacks that could fundamentally alter critical processes.

The Freemium Fallout

If this PLC malware variant isn’t on the table for malicious actors to use and abuse, what’s the big deal? Abbasi can release his findings and the problem will be patched, right? Not quite. According to Softpedia, there’s a new trend emerging in the malware market known as freemium software.

The concept has been around for decades in legitimate software circles. According to this play-before-you-pay approach, users get stripped-down versions of software that showcase some of the most useful features. If they want the full offering, they need to pay.

Now malware-makers are following suit. One Italian malware developer known as Viotto is offering a free version of a keylogger to would-be cybercriminals. While it won’t do as much damage as, say, Mirai, it’s a worrisome precedent, especially since these new malware offerings are effectively fire-and-forget.

In the hands of Abbasi and a handful of researchers, these new exploits are no big deal. Freemium versions used by millions of malicious hangers-on, however, could mean big trouble for the cybersecurity industry.

Getting Ahead of PLC Malware

PLC malware is evolving. Security researchers hope to solve processor problems now, before the next generation of IoT-enabled controllers hit the market, but it’s a race against time. With cybercriminals developing a freemium distribution model, the distance between the lab and the wild just got a whole lot shorter.

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