Researcher creates tools to switch off PLCs

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Researcher creates tools to switch off PLCs

System runs online without authentication.

A researcher has revealed dangerous holes in a supervisory control and data acquisition (SCADA) system used by some 261 manufacturers including Bosch, CAT and Mitsubishi Electric Europe.

By taking advantage of an absence of authentication and tendency to run the Codesys ladder logic runtime engine as root, an attacker could wipe memory from a Programmable Logic Controller (PLC) running the platform, start and stop the ladder logic and peruse files and directories.

They could also use in-built functions to send and receive files and, via a directory traversal flaw, could read and write files outside of the Codesys system.

"On most operating systems this includes the ability to overwrite critical configuration files such as /etc/passwd and /etc/shadow on linux, or the windows registry on Windows CE," Digital Bond researcher Reid Wightman wrote.

The affected functions within the runtime engine included a TCP file transfer service and command line interface that Wightman found did not require authentication. 

The Codesys runtime engine was also vulnerable because its design ensured it was typically run as root or on operating systems with poor security controls.

Wightman demonstrated the flaws on a WAGO embedded computer PLC, but said the attacks would likely work on all Codesys PLC makes and models. 

He said the only security offered by the Codesys platform were checks which tested if it was communicating with the correct PLC.

Wightman and a colleague released a pair of Python tools to interact with PLCs running the vulnerable Codesys platform.

Both tools, including a command shell utility that grants privileges to unauthenticated attackers, could be ported to Metasploit.

"It is the equivalent of running the PLC browser function from the Codesys desktop software, but does not assert vendor checks normally performed by the Codesys software — Codesys will normally fail to connect to a PLC and offer this option without properly licensed plugins," Wightman said.

Wightman also released a file transfer tool for reading and writing files on controllers with a filesystem.  

The creators of Codesys 3S Software Gmbh did not respond to requests for comment by the time of publication.

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