Monthly Archive for August, 2010

A Threat Analysis of Networked Medical Devices

Here’s an interesting analysis of security threats within a Windows-based hospital network for embedded medical devices: A threat analysis of critical patient monitoring medical devices.

The threat models are fairly complex and clearly a product of wider enterprise network IT security needs. I’ve discussed some of the other issues of putting medical devices on an institutional network in Networked Medical Devices. Security threats were not covered and this is an important topic for every hospital network.

There are a couple of items in this article worth commenting on.

The top five unmitigated threats were found to be:

The corrective action for the top threat (T002) was (my highlight):

After it was decided to remove all ePHI from the medical device data storage, the risk assessment changed and the threat of the medical device infecting the hospital enterprise network (T017) then became our primary concern.

This may be the “most effective countermeasure possible for HIPAA compliance and protecting patient privacy”, but it is a not practical solution in the real world. Many medical devices store patient demographics. Because the benefits of patient identification outweigh the security risks, this practice is not likely to change in the future.

On these questions:

  1. Can the medical devices be infected from the enterprise network?
  2. Can the medical devices be infected via removable media?
  3. Can infected medical devices propagate malicious software back into the enterprise network?

I generally agree with the conclusions for the device under analysis. The challenge for a hospital is how do you ensure that every networked medical device follows these best practices (communications integrity, hardened OS, clean distribution media, etc.)?

Technical Debt in Medical Software

Software development is software development. Most of the life cycle and quality issues faced in medical software are the same challenges for any software product. Technical Debt in Medical Software points out what technical debt is:

  • Complexity
  • Code Duplication
  • Documentation Debt
  • Testing Debt
  • Architectural Debt

A Martin Fowler article is referenced that nicely identifies the source of technical debt:

The benefits of paying down the debt are:

  • Increased R&D efficiency and improved time to market
  • Hitting commitment dates
  • Performance and technology upgrades

Of course if you don’t want to pay it off, there’s always the option to go bankrupt. This may have long-term advantages, but it will surely be a more expensive route. There is one statement in this regard that I think needs some qualification:

In this case the technical debt can be retired along with the legacy system, and like filing Chapter 11, you are no longer responsible to address all the sins of the past.

I know this refers to code sins, but just because you decide to do a re-write doesn’t mean you no longer have responsibility for the legacy product. You still have customers using the old software that you’re obligated to continue to support.  For FDA approved medical software, this is a legal requirement. Most of the time this means that the legacy code will need to be maintained and periodically updated in the field, sometimes even after the “new” product is released. This just makes the cost of bankruptcy even higher.

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