Checksum & Signature Databases
	Ø They contain a unique value for a mail message that depends on the msg content Ø If the content is different, so is the value Ø What content is used and how much it has to change for the computed value to change depends on the database Ø Used to compare the computed value of a new message against the value of known spam messages to identify spam Ø The spam determination is usually made by counting reports for the same value