Our dual scanning virus protection scans all inbound
and outbound emails using a multi-stage, dual scanner
process. The process is broken down into the following
four stages:
Dual
Scanning Virus Protection
Stage 1: Restricted Attachments
Here, emails are scanned for dangerous types of
file attachments. When an email is sent or received
that contains a restricted file attachment, the
email is rejected and the sender receives a "bounced"
email notification informing them of the restriction.
Stage 2: Normalization
This stage searches for email formatting vulnerabilities
that can be used by viruses to hide from virus scanners.
If any vulnerability is found, our system corrects
the formatting of the message so that it can be
thoroughly scanned for viruses.
Stage 3: Decompression
Next, if the email contains any compressed attachments
such as zip files, the compressed attachments are
temporarily unzipped so that the contents can be
scanned for viruses.
Stage 4: The Dual Virus Scan
After the above preprocessing is complete, two
separate virus scanners are used to scan the email
and all of its uncompressed attachments. Everything
is scanned twice to ensure maximum protection
against new virus threats. ClamAV (www.clamav.net)
and F-Prot (www.f-prot.com) are the current scanners
of choice, although our system was designed to
be able to plug-in any virus scanner on the market,
should the need to do so arise.