Dynamically protecting against web resources associated with undesirable activities

Various embodiments provide protection against web resources associated with one or more undesirable activities. In at least some embodiments, a method detects and responds to a user-initiated activity on a computing device. Responding can include, by way of example and not limitation, checking locally, on the computing device, whether a web resource that is associated with the user-initiated activity has been identified as being associated with a safe site. Furthermore, in at least some embodiments, the method checks remotely, away from the computing device, whether the web resource is identified as being at least possibly associated with one or more undesirable activities.