Utilities Facing Brute-Force Attack Threat

SSH attack warning from ICS-CERT just the latest in a series of high-profile vulnerabilities affecting critical infrastructure of power plants, hospitals, even prisons.

Another day, another SCADA threat: ICS-CERT is now warning utilities and other critical infrastructure providers about potential brute-force attacks against control systems with SSH command-line access.

For an industry that traditionally has been cloistered and unaccustomed to cybersecurity threats to its systems, it has been a rough few months, with several security researchers exposing and poking some serious holes in the products that run in power plants, manufacturing floors, hospitals, and even prisons. Most recently, Metasploit late last month added a new exploit to the Metasploit Framework for an attack demonstrated by Digital Bond against the GE D20 PLC device. Other SCADA product exploits by the Digital Bound researchers are also in the works for Metasploit, including ones for Rockwell Automation, Schneider Modicon, and Koyo/Direct LOGIC. Last summer, researcher Dillon Beresford demonstrated a backdoor in Siemens S7-300, S7-400, and S7-1200 devices that allowed him to get inside and capture passwords and reprogram PLC logic in such a way that he could shut down the systems altogether or cause them to eventually crash.

ICS-CERT reported on Friday that many organizations have been witnessing secure shell (SSH) scans of their Internet-facing control systems, including an electric utility that told ICS-CERT it had been hit by some brute force attempts against its networks that were "unsuccessful." The attackers are probing Port 22/TCP, the default SSL listening port, to look for SSH. Once they get a response from the probe, they can execute a brute-force attack for login credentials in order to acquire remote access.

It's an attractive attack vector because many control-system devices on networks run SSH by default. ICS-CERT recommends monitoring network logs for port scans and access attempts. "Hundreds or thousands of login attempts over a relatively short time period is an indicator of a brute force attack because systems running SSH normally do not receive high volumes of login attempts," the ICS-CERT alert says. "However, indication of an attack does not necessarily mean that the organization is the actual intended target. Scans are frequently executed against a wide range of IP addresses looking for any system meeting the attacker’s criteria (in this case, systems running SSH)."

This is just the latest in a string of painfully simple hacks to which critical infrastructure providers are vulnerable. Researchers Billy Rios and Terry McCorkle during the past year have been reporting bugs they find in industrial control systems products: They've found more than 1,000, of which 98 are easily exploitable. Among the most obvious bugs they found were via human management interface (HMI) applications that were accessible via the Internet, as well as file format and ActiveX flaws.

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