George Ou writes about a possible exploit of MS Vista's speech recognition system, describing a scenario where spoken words played by an application (or web site) were able to engage the OS's voice recognition system. So if your computer reacts on spoken words - beware. Don't use these:
"Shutdown."
"Encrypt / Wipe / Format disk."
"Send mail to all known users."
"Quit, don't save."
"Activate Windows."
"Change Password to #%+&$#-§$)."
"Switch on web cam. Publish."
"Make share c$, allow for everyone."
"Run http://badwebsite.com/badsoftware.exe".
"Say: I must not let my Windows speak!"