Security bugs on the German manufacturer's Simatic Step 7 and Simatic PCS 7 SCADA control software created a means to load malicious dynamic-link library (DLL) files. This is the type of flaw exploited by the Stuxnet worm, which used DLL hijacking techniques in Step 7 software to infect systems controlling high-speed centrifuges at Iranian nuclear facilities. It is not clear, however, whether or not this specific bug was used in the Stuxnet attack.
Siemens said that previous versions of its Step 7 and PCS 7 software allowed the loading of DLL files into the Step 7 project folder without validation – giving the malware free rein to attack the SCADA systems. The firm fixed the flaw by introducing a mechanism that rejected the loading of DLL files into the folder – effectively blocking the path to possible infection, an advisory by the Industrial Control Systems Cyber Emergency Response Team (ISC-CERT) explains.
A second update, also released on Monday, deals with a SQL server authentication security flaws in Siemen’s Simatic WinCC and Simatic PCS 7 software. Left unfixed, the vulnerability created a means for hackers to get into targeted systems using default credentials.
Siemens issued a series of patches in the wake of the discovery of the Stuxnet worm back in 2010 but this failed to placate critics, including Ralph Langner, who claimed last year that many shortcomings in Siemens' supervisory control and data acquisition (SCADA) systems remained unpatched.
Stuxnet used an array of Windows-based zero-day flaws, configuration weaknesses and security bugs in SCADA systems to infect a system and spread across it. So even though the main Windows-based attack vector was patched relatively quickly, concerns remain about the security of industrial controls software, which is often overlooked when it comes to patching.
read more: http://www.theregister.co.uk/2012/07/25/siemens_scada_security/
