Web Service and Security advice

I'll explain our network configuration first. We have two zones in our firewall. The Green zone and the Orange zone. The green zone is our internal network that is not accessible from anything on the outside. The orange zone has one IIS that is accessible from the outside. We can access everything in the orange from the green. That being said.  I have web applications that run in the orange zone for our registered uses to access. These applications utilize the same data that is stored in our main database that resides in the green zone.  Right now I use DTS jobs to transfer the data I need to another SQL server database in the Orange zone so my web app can get to it.  This seems redundant to me, and I am finding that we need to access more and more data, requiring more and more DTS jobs.  I have data going every which way because I have to DTS data from the orange that is generated by the web app back to the green zone to live in the main database.
Whew! I am proposing to management that we utilize web services to provide all the data we need to apps that run inside the green zone and orange zone.  I want to use the web service to access the main database in the green zone for everything.  The only problem is, when they ask what the security consequences are, I can't really answer.  I know we can open a port up in the firewall to allow either the web services to get to the database, or run the web service with in the green and allow the app to access the web service.  I know other companies must have the same problem. I'm looking for a network configuration example, or what the best approach would be.  Hopefully I've provided enough information. If not please let me know. All systems are MS except for our firewall with is Linux(smoothwall)
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<paranoia mode>
You must always be sure that a complete, call it hijack, of the webserver, credentials, everything, does not enable an attacker or malicious user to perform any queries on the database directly.

If you directly allow the webserver to perform queries on the database tables, then that database server is very susceptible to vulnerabilities in the web server. In the worst case, an attacker can control the webserver, get the credentials, and perform any query on the database server. Theoretically, worst case.

A more secure setup is an application proxy that sits between the web server and the file server. Usually, this application proxy is separated from the web server by another firewall and it only allows, let's say, SQL queries in.

The web server sets up an authenticated session to the application proxy, which defines exactly what the web server can do in that session; for example, change specific columns of records or delete a single record at a time. The application proxy exposes no feature to nuke a random table.

Such an application proxy is usually not an out-of-the box solution and depends completely on the type of database and web application in front of it. But that's how it should work.


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ChadMarshAuthor Commented:
Thanks. That gives me a place to start.
Alright, you're welcome.
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