This occurs when someone other than the owner is using the computer, most often with the owner's permission. When you give someone access to a computer registered to you, you are taking responsibility for their actions on the Harvard network. Even if they used the computer on another network, they may have left file-sharing software running in the background. For assistance in de-registering computers you no longer use, checking for background software, and securing your computer from unauthorized use, please contact your local help desk. There are many steps that all personal computer owners should take to secure their systems. Harvard University Information Technology has posted a checklist of the most important steps at: http://huit.harvard.edu/faq?page=4 . Harvard expects users to take reasonable precautions to secure their personal computers, and individuals may be held responsible for misconduct that occurs from others' use or misuse of their systems. If you receive a copyright violation notice and suspect that your computer has been compromised, please contact your local help desk or network administrator for assistance.