In my last post you would have noticed that Exchange 2007 comes with additional protection in the form of agents. Maybe someone at Microsoft is a big fan of the Matrix I dont know. But i briefly wanted to cover agent roles on the Edge Server…
Additional layers of message protection and security are provided by a series of agents that run on the Edge Transport server and act on messages as they are processed by the message transport components. These agents support the features that provide protection against viruses and spam and apply transport rules to control message flow.
Edge Transport Rules
Edge Transport rules are used to control the flow of messages that are sent to or received from the Internet. The Edge Transport rules help protect corporate network resources and data by applying an action to messages that meet specified conditions. These rules are configured for each server. Edge Transport rule conditions are based on data, such as specific words or text patterns in the message subject, body, header, or From address, the spam confidence level (SCL), or attachment type. Actions determine how the message is processed when a specified condition is true. Possible actions include quarantine of a message, dropping or rejecting a message, appending additional recipients, or logging an event. Optional exceptions exempt particular messages from having an action applied.
You use address rewriting to present a consistent appearance to external recipients of messages from your Exchange 2007 organization. You configure the Address Rewriting agent on the Edge Transport server role to enable the modification of the SMTP addresses on inbound and outbound messages. Address rewriting is especially useful when a newly merged organization that has several domains wants to present a consistent appearance of e-mail addresses to external recipients.
Edge Rules Agent
The Edge Rules agent, which runs on the Edge Transport server, helps you control the number of unwanted messages that enter your organization. If your internal network is compromised, the Edge Transport rule agent can also apply the same or different rules to outgoing messages. In this manner, the Edge Rules agent helps you prevent infected or unwanted messages that are generated by infected computers in your internal network from leaving your organization. The following list provides some examples of when the Edge Rules agent can help you protect your organization:
Virus outbreaks Thousands of new viruses are created each year. Most antivirus software providers are reactive when they update their software. To update their software, antivirus software providers have to identify the virus, create an update for their software, and then send the update to their customers. This causes a gap in protection where an infected message can enter an organization unexpectedly.
Denial of service attacks Malicious individuals who want to do harm to organizations may use denial of service (DoS) attacks to draw attention to themselves or to cause damage. These attacks are typically unannounced and can be difficult or impossible to predict.
The Edge Rules agent is designed to help you reduce the impact of each of these risks. The Edge Rules agent lets you configure conditions and exceptions to identify both unwanted and wanted messages and to act on those messages by using configured actions.
Anti-Spam and Antivirus Scanning
In Exchange 2007, the anti-spam and antivirus features provide services to block viruses and spam, or unsolicited commercial e-mail, at the network perimeter. Most viruses use spam-like tactics to gain access to your organization and to entice users to open an e-mail message. If you can filter out most of your spam, you are also more likely to capture viruses before they enter your organization.
Spammers use a variety of techniques to send spam into your organization. Servers that run the Edge Transport server role help prevent users in your organization from receiving spam by providing a collection of agents that work together to provide different layers of spam filtering and protection. Establishing tarpitting intervals on connectors makes e-mail harvesting attempts ineffective.
The Sender ID agent
The Sender ID agent relies on the RECEIVED Simple Mail Transfer Protocol (SMTP) header and a query to the sending system’s domain name system (DNS) service to determine what action, if any, to take on an inbound message.
When you configure anti-spam agents on an Edge Transport server, the agents act on messages cumulatively to reduce the number of unsolicited e-mail messages that enter the organization.
Sender ID is intended to combat the impersonation of a sender and a domain, a practice that is frequently called spoofing. A spoofed mail is an e-mail message that has a sending address that was modified to appear as if it originates from a sender other than the actual sender of the message.
Spoofed mails typically contain a From: address that purports to be from a certain organization. In the past, it was relatively easy to spoof the From: address, in both the SMTP session, such as the MAIL FROM: header, and in the RFC 822 message data, such as From: “Michael Smith” Michael@mydomain.com, because the headers were not validated.