DEF CON 20 -- Las Vegas, NV -- A pair of Russian researchers poised to reveal new research and release free tools for breaking into power plants were no-shows here today.

The much-anticipated "SCADA Strangelove: How I Learned To Start Worrying And Love The Nuclear Plants" talk was quietly replaced a week ago with another presentation by researcher Wesley McGrew on HMI interface vulnerabilities in process control systems, much to the surprise of attendees.

According to the description of their talk in the Def Con program, Sergey Gordeychik and Denis Baranov were scheduled to unleash some 20 new vulnerabilities in popular SCADA systems, including Siemens Simatic WinCC. They were also geared up to release three tools: modbuspatrol (mbpatrol), which fingerprints programmable logic controllers; a Simatic WinCC security checklist; and an exploit for a Simatic WinCC-based power plant. Simatic WinCC was one of the products targeted by the infamous Stuxnet worm, which reportedly was launched by the U.S. and Israel.

The researchers, who are with Positive Technologies, were planning to demonstrate how to gain access to power plants via a sniffer and packet generator, FTP and Telnet, Metasploit and oslq, and a Web server and browser.

It's unclear why the talk was cancelled: Neither the researchers nor Siemens were available for comment at the time of this post, and Def Con officials say the speakers pulled their presentation from the lineup about a week ago. McGrew said in a tweet late today that it was "nothing sinister."

Both Def Con and Black Hat conferences are no strangers to potentially bombshell presentations getting pulled at the last minute. Given the sensitive nature of the talk, it's likely the researchers were pressured by the affected SCADA vendors not to reveal their hacks and unleash their tools for fear they could fall into the wrong hands.

"Researchers I know who look into SCADA bugs complain about vendor pressure, and even government pressure, so it's a reasonable hypothesis," says Robert Graham, CEO of Errrata Security.

"I had the FBI come threaten me to stop a talk that isn't as scary as 20 SCADA bugs," Graham says.

[Firewall, VPN features now embedded in some products as Siemens gradually beefs up its security strategy. See Siemens Enhances Security In Post-Stuxnet SCADA World. ]

Meanwhile, the show went on, with research presented on easy-to-find and exploit holes in HMI interfaces of SCADA systems. Wesley McGrew, research associate with Mississippi State University, revealed a handful of reported vulnerabilities in HMI products, including KEP Infilink-HMI 5.00.23, KingView 6.5.3, and Iconics Geensis32 9.2.2 -- all of which come from weak user authentication.

"These are not Pwnie Award-winning attacks -- they are not hard to do," McGrew says. "But they require some level of access [to the machines] and are part of a larger attack."

With "a lot of these, you encrypt the password with the same key for every user and every installation," he says.

These attacks are mostly insider threat ones, including air gap-hopping like Stuxnet was, McGrew says. "You could have users doing it intentionally or unintentionally, and basically hopping air gaps," he says. "Even if the air is there, nothing in insurmountable. A lot of times the user doesn't know whether there is an air gap."

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