SpamShark

Blacklisting of websites & domains:
Catalog.com maintains an up to date list of the largest and most aggressive known spammers. This list is maintained by both Catalog.com and other anti-spam groups.

Keyword scanning of emails:
Scanning methods include a scoring system such that emails are scored based on a number of criteria. If the score is above a threshold, then that email is flagged as spam.

Checksum technology:
Our system monitors email traffic through the Internet and uses checksum technology to keep track of the number of times a particular message has appeared on the Internet. If a message has appeared over a certain number of times, it is categorized as known spam.

Message authenticity checking:
Several algorithms are utilized to verify the authenticity of a message. Some of these are simple checks to verify that the “from address” is authentic. Some are more complex relating to SMTP protocol.

Rate controls:
Utilized to stop denial of service attacks as well as dictionary based spam attacks.

File type attachment blocking:
Harmful scripts (Viruses) are blocked.