Last year, the Stuxnet worm made big news in the industrial controls community (see IEEE Spectrum, 2010-11 issue). It was the first worm specifically targeted to Supervisory Control and Data Acquisition (SCADA) systems. It modifies code on PLCs to take control of them.

Worms get into control systems almost exclusively through human error. For example, someone violates control system rules and uses a USB drive. And if the drive happens to be infected….

The most common means of entry is through a security door left wide open with weak logons or passwords. If, for example, your logon is "Admin" you need to change it. Typically, the IT department informs users about security measures, and yet users don't comply because "it’s a hassle." Indifference to security is a form of sabotage, and companies have the right to terminate employees with that attitude.

While the maintenance department typically doesn't do the IT function, it's the maintenance department that is going to get the call when things stop working in the plant. In our next issue, we'll look at some worm prevention and mitigation steps you can take.