The Official Pattern Release or OPR is Trend Micro's latest compilation of patterns for identified viruses. It is guaranteed to have passed a series of critical tests to ensure that customers get optimum protection from the latest virus threats. Editors Note: Most people do not need to download the latest definition files, but rather use your anti-virus programs auto updater to get daily updates as soon as they are available. This download is provided here in case you are having trouble with your auto update feature.