Basically, no. You do not need Forefront. The reasons for this are that if you have 2 FE environment using the same physical SQL server, they do not use the same database so data stored in your production database will not be accessed from your development environment and vice versa. Also, sharepoint really is not at risk from viruses. It is the client systems which are at risk as a virus needs to be opened in such a way that it can execute the malware. Sharepoint only actually reads the documents stored inside it when it indexes the database for future searches. During this indexing process, the documents are not actuall opened but the binary data is passed from sql to sharepoint and the text of the document extracted. As this is simple text it does not have the possiblity to execute any code. I hope this answers your query.