These things really are contagious

Everyone knows viruses can disrupt office networks, but they also can bring production systems down, even if hackers don't directly target a shop-floor network.

Most viruses enter corporate networks via e-mail, which is why Ontario-based Nemx Software created Power Tools for Microsoft Exchange, a suite of filtering applications for the most widely used e-mail server.

With these tools in place, any message that hits an e-mail server can be scanned for viruses or screened as possible spam. Network administrators decide how offending messages are handled. Typical actions for viruses include cleaning the file before letting it through, or placing the file in quarantine until the named recipient can identify the sender.

John Young, president of Nemx Software, contends such filtering limits the possibility of viruses creeping onto a shop-floor network, although he says the best safeguard would be a series of partitions that prevent anyone from sending data that is not germane to the manufacturing process to any shop-floor systems. He also says there's an art to partition building.

"You could build partitions that prevent any data from getting from your corporate network to the production network, but that would slow down your business as well. Instead, you have to know what data needs to go where and make sure you enable and disable the proper connections."