Spam Filtering and Virus Protection

Spam Filtering

It is estimated that 85% of all email traffic on the Internet is spam. Spammers are growing wiser on a daily basis, learning new methods to manipulate common spam defences and obtaining more sophisticated software to trick spam filters and penetrate email inboxes. In order to win the war against spam, businesses must evolve their spam defences faster than spammers evolve their techniques.

Our Spam Filtering system accomplishes this by gathering real-time spam intelligence from a number of sources and then actively using this intelligence to block the spam. We track tens of thousands of live spam email characteristics ("DNA"), which alone identify the majority of spam. In addition, a number of third-party spam databases, several DNS checks, and several message-formatting tests are used when analysing each email. We aggregate all of this data into a collection of several thousand constantly evolving spam tests that are performed on every email that enters the email hosting system.

The results of these tests are combined together to identify more than 98% of spam with virtually zero false-positives.

Filtering Highlights

  • Thousands of email characteristics ("DNA") are used to identify spam
  • 25 third-party spam databases, several DNS checks, and message-formatting tests are also used when analysing each email
  • DNA and other data are used to perform more than 45 tests on every email
  • Tests are combined into a weighting system and assigned a value
  • When the total weight of an email is greater than a certain sensitivity threshold it will be flagged as spam
  • Integrates with Return Path and Bonded Sender to minimize false-positives

User Controls

Virus Protection

Our virus protection scans all inbound and outbound emails using a multi-stage process. The process is broken down into the following four stages:

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: Normalisation
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: Virus Scan
After the above preprocessing is complete, a virus scanner is used to scan the email and all of its uncompressed attachments. Everything is scanned to ensure maximum protection against new virus threats.

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