When conducting anti-virus, anti-spam, or other content filtering on a gateway device, data traffic is run through a proxy that completes a “fetch-scan-forward” operation of the data traffic exchanged between a server and a client. During the transmission of data from the server to the proxy and while the gateway is scanning the data, the client is idle and in danger of timing-out and aborting the data request to be received from the proxy. To prevent this, the proxy sends an intervention message, typically in the form of an extension header file, continuation response, and/or innocuous command, in advance of the client-side time-out. Alternatively, during the transmission of data from the client to the proxy and while the gateway is scanning the data, the server is idle and in danger of timing-out. A proxy sends an intervention message, in the form of an innocuous command, in advance of the server-side time-out.