When you get down to brass tacks, it is the fact that Internet Information Services (IIS) -- which includes the HTTP, NNTP, SMTP, IMAP4, POP3 and a number of other Internet protocols -- is the source of vulnerability. However, you can not install Exchange 2000/2003 without it running.
The real risk is not planning for it. Here is a short list of things you can do to secure Outlook Web Access.
- Implement Secure Socket Layer (SSL) for secure HTTPS communications between the client (browser) and the server.
- Use front-end servers for Internet clients to connect to. No data is stored on the front-end server and therefore it is a lower risk if compromised.
- Implement IPsec between front-end and back-end servers. SSL can't be used between front-end and back-end servers, but IPsec can.
SSL is really the key to securing Outlook Web Access. You should not allow clients to connect to Outlook Web Access without using SSL.
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This was first published in July 2005