NoSpamToday! for Servers - Attachment Filter

Blocking malicious attachments

Most worms and viruses are spread by attachments. Getting rid of messages containing potentially malicious attachments before even starting virus checkers or spam filters can be very helpful to reduce system load.

NoSpamToday!'s built-in attachment blocker allows you to specify a list of attachments that you want to accept, or, the other way round, you can specify a list of attachments you do not want to accept. The attachment filter is pre-configured to reject all attachment types known as potential virus vectors.

The attachment blocker is also capable of detecting MIME violations. MIME violations can disrupt mail server operation and sometimes crash mail clients. Also, worm authors could try to hide executable attachments with deliberate MIME syntax violations.

Attachment Filter Configuration Options

NoSpamToday!’s built-in attachment blocker allows you to specify a list of attachments that you want to accept, or, the other way round - you can specify a list of attachments you do not want to accept. The attachment filter is pre-configured to reject all attachment types known as potential virus vectors.

MIME Error Policy Options

• General MIME syntax violation (SEVERE): Worm authors could try to hide executable attachments with deliberate MIME syntax violations.
• ASCII-0 character (SEVERE): The mail contains an ASCII-0 character. This problem can disrupt mail server operation and sometimes crash mail clients.
• Line Break Error: The message has a single carriage return or line feed character in the message or a line is too long. These MIME violations are very common in spam messages, but also sometimes present in legitimate messages.
• 8-bit character in header: This MIME violation is very common and, for this reason, only reported in the log.

For severe MIME violations, we recommend deleting messages. You can choose a different setting, if desired. The policy you apply has to be chosen with the MIME Error Policy setting.

The Line Break Policy setting controls the handling of wrong line breaks. Messages with wrong line breaks are passed by default.

Learn More ...

• Read more about NoSpamToday!'s Delay Filter.
• Read more about NoSpamToday!'s Mail Flooding Protection and Traffic Limiting.
• Read more about NoSpamToday!'s Open Relay Protection.
• Read more about NoSpamToday!'s Core Features and Benefits.