Anti-virus scanning of partially available content

A client device transmits requests via a gateway to a server in a network environment. The requests indicate specific portions of a file on a server to be transmitted as part of the download process. The gateway receives into its memory the requested portions of the file and assembles the received portions into an assembly file. The gateway continuously scans the largest contiguous sequence of the portions in the assembly file for viruses while the requested portions of the file are being received and become available before feeding the received portions to the client computer. By scanning the largest consecutive sequence while new portions become available, the time to complete the scan is reduced thereby increasing the throughput of the gateway.