The script channel is similar to the conversion channel in that arbitrary processing can be done on messages flowing through PMDF. The difference is that the script channel passes the entire message to the command procedure or script, instead of body part by body part. As with the conversion channel, any set of programs or command procedures can be used to perform script channel processing. For instance, third party virus or spam scanning software may be hooked in for automatic execution via the script channel. Or sites may develop their own custom applications to hook in.