There has been a fair amount of traffic regarding the security issues of applications like the Google desktop on the IT side in the last several months.
Within the ACS SCADA world (Update to fix spelling) you should consider the implications of the desktops but also the Google appliances. These devices are being installed by many organizations to simplify everything from Intranet Website development to E-discovery. Like most Google products they are very good at what they do.
The thing to keep in mind with them is that they are web crawlers on steroids. They don't just hit HTTP they also chase down many other file sharing and transfer mechanisms. Look at the databases they crawl as well. They will find Windows shares. They follow links and scan address ranges to index and cache data. They can be configured to limit the extent of the scan but in many cases this is haphazardly done.
Many PLC's have http interfaces now and all of the Historians I know about have some flavor of Db.
This takes on particular concern when placed in context of our recent discussions on the possible impacts of scanning.
Scanning Vs Not Scanning
More Scanning - Be careful
Ramifications of Scanning
and keep this in mind when considering what Securosis had to say.
The good news is that the vendors are getting better at designing these interfaces to be resilient.