Руководство Пользователя для Cisco Cisco Email Security Appliance C170

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Cisco IronPort AsyncOS 7.1 for Email Configuration Guide
OL-22158-02
Chapter 9      Anti-Virus
) for detecting viruses, 
the multi-scan approach can be even more effective. Using multiple scanning 
engines can lead to reduced system throughput, please contact your IronPort 
support representative for more information.
You cannot configure the order of virus scanning. When you enable multi-layer 
anti-virus scanning, the McAfee engine scans for viruses first, and the Sophos 
engine scans for viruses second. If the McAfee engine determines that a message 
is virus-free, the Sophos engine scans the message, adding a second layer of 
protection. If the McAfee engine determines that a message contains a virus, the 
IronPort appliance skips Sophos scanning and performs actions on the virus 
message based on settings you configured. 
Sophos Anti-Virus Filtering
The IronPort appliance includes integrated virus-scanning technology from 
Sophos, Plc. Sophos Anti-Virus provides cross-platform anti-virus protection, 
detection and disinfection. 
Sophos Anti-Virus provides a virus detection engine that scans files for viruses, 
Trojan horses, and worms. These programs come under the generic term of 
malware, meaning “malicious software.” The similarities between all types of 
malware allow anti-virus scanners to detect and remove not only viruses, but also 
all types of malicious software. 
Virus Detection Engine
The Sophos virus detection engine lies at the heart of the Sophos Anti-Virus 
technology. It uses a proprietary architecture similar to Microsoft’s COM 
(Component Object Model), consisting of a number of objects with well-defined 
interfaces. The modular filing system used by the engine is based on separate, 
self-contained dynamic libraries each handling a different “storage class,” for 
example, file type. This approach allows virus scanning operations to be applied 
on generic data sources, irrespective of type.
Specialized technology for loading and searching data enables the engine to 
achieve very fast scanning speeds. Incorporated within it are:
a full code emulator for detecting polymorphic viruses