Handling Large Files

IWSVA provides the following methods to address large-file scan lag:

• Do not scan files larger than... IWSVA will not scan files larger than the size specified.

• Caution: This option effectively allows a hole in your Web security -- large files will not be scanned. Trend Micro recommends that you only choose this option on a temporary basis.  

• Enable special handling when a file is larger than Only enable this option if you are experiencing a problem with client browser time-outs or otherwise need to improve file and page-delivery performance.

• Scan before delivering—(lowest risk, HTTP Scanning only) Default. Requesting clients may experience a noticeable delay in page loading and file transfer times. During the lag time, clients will see a progress bar in their browser window while IWSVA downloads, scans, and delivers the file.

• Deferred scanning—(moderate risk) IWSVA receives the file from the proxy server and begins scanning. To keep the client connection alive for the time it takes to scan the large file, IWSVA "trickles", or delivers a small amount of the file to the requesting client. This option is considered "moderate risk" because it is possible that malicious code will be delivered to the client machine as part of the unscanned delivery.
  
  Most files, however, are unreadable until the entire file is reconstructed.