To provide the best possible security, Avast employs a complex ecosystem of detection techniques. Whenever a file enters your computer or gets executed in your computer, a sequence of checks is performed usually in a fraction of a second. The majority of malicious files get discovered using fast detectors running with a small footprint in your computer. Occasionally, however, these detectors can’t reliably assess a file (this can be the case if it is new and unique). In these scenarios, the cloud backend comes to the rescue, since it’s capable of running deep extensive tests that make use of all the knowledge that Avast has. Such extensive tests are done using so much computing power and data that a standalone computer with installed antivirus would not manage to handle it. The interplay of the client-side antivirus engine and its cloud backend ensures that all files get detected with the maximum achievable accuracy.