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InterScanTM Messaging Security Virtual Appliance - Online Help ...

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Trend Micro InterScan <strong>Messaging</strong> <strong>Security</strong> <strong>Virtual</strong> <strong>Appliance</strong> Administrator’s Guide<br />

9-14<br />

• Duration to monitor: The number of hours that IMSVA monitors email<br />

traffic to see if the percentage of email messages with viruses exceeds the<br />

threshold you set.<br />

• Rate (%): Type the maximum number of allowable email messages with<br />

viruses (the numerator).<br />

• Total mails: Type the total number of infected email messages out of which<br />

the threshold percentage is calculated (the denominator).<br />

• Threshold: The maximum percentage of email messages with virus threats<br />

that IMSVA will allow during the value you set for Duration to monitor above.<br />

The threshold is a fraction with a numerator and denominator:<br />

• Rate (%): Type the maximum number of allowable email messages with<br />

virus threats (the numerator).<br />

• Total mails: Type the total number of virus email messages out of which<br />

the threshold percentage is calculated (the denominator).<br />

Consider the following example.<br />

Duration to monitor: 1 hour at a rate of 20 out of 100<br />

During each one-hour period that virus blocking is active, IMSVA starts<br />

blocking IP addresses when more than 20% of the messages it receives contain<br />

viruses and the total number of messages exceeds 100.<br />

5. Next to Triggering action, select one of the following:<br />

• Block temporarily: Block email messages from the IP address and allow the<br />

upstream MTA to try again.<br />

• Block permanently: Never allow another email message from the IP address<br />

and do not allow the upstream MTA to try again.<br />

6. Click Save.

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