A method for de-anonymizing online visitors or contacts by mapping anonymous Internet Protocol, IP, addresses to known accounts the method comprising using at least one hardware processor of a server platform to: receive a plurality of events from a plurality of sources, wherein each of the plurality of events represents an online activity and comprises an IP address and event information; aggregate subsets of the plurality of events into a plurality of mappings, wherein each of the plurality of mappings associates the IP address, shared by a subset of the plurality of events, with an account, and is associated with a plurality of statistics regarding the subset of events; for each of the plurality of mappings, compute a confidence value for the mapping based on the associated plurality of statistics, wherein the confidence value for a particular mapping represents a measure of confidence that a visitor or contact, who has used, is using, or will use the respective IP address throughout an online activity, is associated with a respective account, wherein computing a confidence value for each mapping based on the associated plurality of statistics comprises calculating a time confidence value, indicating a timing of events from which the mapping was derived, calculating a statistical confidence value, indicating a frequency of the events from which the mapping was derived, calculating a source confidence value, indicating an accuracy of one or more of the plurality of sources from which the events, from which the mapping was derived, were received, and calculating the confidence value based on the time confidence value, the statistical confidence value, and the source confidence value; select a final subset of the plurality of mappings based on the confidence values for the plurality of mappings, wherein a mapping is selected only if its confidence value exceeds a predetermined minimum threshold; and respond to one or more requests, comprising a requested IP address, by searching the final subset of mappings for the requested IP address, and returning an indication of an account associated with the requested IP address in the final subset of mappings and the associated contact information for that account enabling to contact the visitor or contact. receive a plurality of events from a plurality of sources, wherein each of the plurality of events represents an online activity and comprises an IP address and event information; aggregate subsets of the plurality of events into a plurality of mappings, wherein each of the plurality of mappings associates the IP address, shared by a subset of the plurality of events, with an account, and is associated with a plurality of statistics regarding the subset of events; for each of the plurality of mappings, compute a confidence value for the mapping based on the associated plurality of statistics, wherein the confidence value for a particular mapping represents a measure of confidence that a visitor or contact, who has used, is using, or will use the respective IP address throughout an online activity, is associated with a respective account, wherein computing a confidence value for each mapping based on the associated plurality of statistics comprises calculating a time confidence value, indicating a timing of events from which the mapping was derived, calculating a statistical confidence value, indicating a frequency of the events from which the mapping was derived, calculating a source confidence value, indicating an accuracy of one or more of the plurality of sources from which the events, from which the mapping was derived, were received, and calculating the confidence value based on the time confidence value, the statistical confidence value, and the source confidence value; calculating a time confidence value, indicating a timing of events from which the mapping was derived, calculating a statistical confidence value, indicating a frequency of the events from which the mapping was derived, calculating a source confidence value, indicating an accuracy of one or more of the plurality of sources from which the events, from which the mapping was derived, were received, and calculating the confidence value based on the time confidence value, the statistical confidence value, and the source confidence value; select a final subset of the plurality of mappings based on the confidence values for the plurality of mappings, wherein a mapping is selected only if its confidence value exceeds a predetermined minimum threshold; and respond to one or more requests, comprising a requested IP address, by searching the final subset of mappings for the requested IP address, and returning an indication of an account associated with the requested IP address in the final subset of mappings and the associated contact information for that account enabling to contact the visitor or contact.