An API call filtering system that filters API calls received, via a network, from user equipments ("UEs") that are network-connected and running endpoint app software and/or hardware, to secure an application programming interface ("API") service that accepts API call requests and provides API call responses thereto, wherein a secured API service is secured against excessive request iterations from a set of rogue UEs while allowing for ordinary volumes of requests of the UEs, wherein a threshold between what is deemed to be an ordinary volume of requests and what is deemed to be excessive request iterations are determined by predetermined criteria, the API call filtering system comprising: memory for storing data; a processor that executes program code; program code for handling requests from UEs, the requests being requests received via a network interface from the UEs; program code for determining a UE installation number ("UEIN") for a received request, and wherein the UEIN is specific to a requesting UE that made the received request, wherein the UEIN of the received request is determined, at least in part, from a personalized API processing of the received request; storage for a plurality of references to UEs, the references being to their corresponding UEINs; program code for verifying with the requesting UE that it is the UE associated with the UEIN included in the request from the requesting UE; and filter controller program code operating, at least in part, by recognizing the UEINs of the requests, the filter controller program code being arranged to: determine whether the received request and prior requests that included the same UEIN as was included in the received request exceed the threshold; allow the API call to reach an API server if the threshold is not exceeded; and block the API call if the threshold is exceeded. memory for storing data; a processor that executes program code; program code for handling requests from UEs, the requests being requests received via a network interface from the UEs; program code for determining a UE installation number ("UEIN") for a received request, and wherein the UEIN is specific to a requesting UE that made the received request, wherein the UEIN of the received request is determined, at least in part, from a personalized API processing of the received request; storage for a plurality of references to UEs, the references being to their corresponding UEINs; program code for verifying with the requesting UE that it is the UE associated with the UEIN included in the request from the requesting UE; and filter controller program code operating, at least in part, by recognizing the UEINs of the requests, the filter controller program code being arranged to: determine whether the received request and prior requests that included the same UEIN as was included in the received request exceed the threshold; allow the API call to reach an API server if the threshold is not exceeded; and block the API call if the threshold is exceeded. determine whether the received request and prior requests that included the same UEIN as was included in the received request exceed the threshold; allow the API call to reach an API server if the threshold is not exceeded; and block the API call if the threshold is exceeded.