Air-gap security an "enduring fairy tale": Byres

Government, vendors and industry need to accept that the dream of an air gap is dead: Byres
  • Stilgherrian (CSO Online (Australia))
  • — 05 July, 2011 10:07

The "air gap" -- the idea that a physical gap between between an industrial control network and an organisation's business network will prevent attacks from reaching critical control systems -- is "one of the most enduring fairy tales in the field", according to leading US critical infrastructure security consultant Eric Byres.

"As much as we want to pretend otherwise, modern control systems need a steady diet of electronic information from the outside world," Byres writes at the Practical SCADA Security Blog.

"Severing the network connection with an air gap simply spawns new pathways -- pathways like the mobile laptop and the USB key, which are more difficult to manage and just as easy to infect," he said. "There is a good reason why you won’t find the air gap mentioned in vendor engineering manuals. As a theory, it is wonderful. In real life, it doesn’t work."

Byres illustrates his argument with the diagram of a high-security network architecture taken directly from Siemens’ Security Concept manual (pg 42).

"Can you spot the air gap in the drawing?" he asks. "Funny, neither can I."

The blog post echoes comments Byres made at the AusCERT information security conference in May, where he speculated that the Stuxnet worm may not necessarily have infected the target supervisory control and data acquisition (SCADA) systems via a USB key.

Byres told the conference that an attacker could mimic the vendor's documentation CD, package it the vendor's stationery, and send it to the manager of the target network. The disc would contain PDF files of real documentation that were infected with Stuxnet.

CSO understands that such a documentation-based attack has already been attempted, although it is believed to have failed.

"Government, vendors and industry need to accept that the dream of an air gap is dead," Byres wrote.

Follow CSO Australia on Twitter: @CSO_Australia

Tags: Air-gap, Byres, Practical SCADA Security Blog, Siemens’ Security Concept manual

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1. Make it clear that the policy is not about playing ‘Big Brother’ but to ensure the security of employees, company information and data and to safeguard the company’s reputation.
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3. Convey the message of flexibility – with regard to social media, it is not about blocking staff usage but working in everyone’s interests to ensure that threats are contained.
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5. Within the training programme make sure that there are specific examples to demonstrate each rule or regulation, and that there is a clear explanation of the dangers of casual or careless talk on social networking sites. Again use examples, employees need to understand the consequences of raising a throwaway comment that has negative connotations for the business, as much as they need to be aware of dangers of making a more direct but ill-considered attack on a competitor, regulator or even a fellow colleague. They need to be clearly advised on any impact on the company and/or legal action or inquires that may be raised as a result.
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9. Enforce the rules – if there is a deliberate or malicious contravening, disciplinary action needs to be taken. A policy isn’t worth having if it is seen to be lax and unenforced.
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Phil Vasic is Regional Director, APAC, at Clearswift, the software security company www.clearswift.com
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