Editing Checksum (section)

==={{anchor|fuzzy checksum}}Fuzzy checksum===
The idea of fuzzy checksum was developed for detection of [[email spam]] by building up cooperative databases from multiple ISPs of email suspected to be spam.   The content of such spam may often vary in its details, which would render normal checksumming ineffective.  By contrast, a "fuzzy checksum" reduces the body text to its characteristic minimum, then generates a checksum in the usual manner. This greatly increases the chances of slightly different spam emails producing the same checksum.  The ISP spam detection software, such as [[SpamAssassin]], of co-operating ISPs, submits checksums of all emails to the centralised service such as [[Distributed Checksum Clearinghouse|DCC]].  If the count of a submitted fuzzy checksum exceeds a certain threshold, the database notes that this probably indicates spam.  ISP service users similarly generate a fuzzy checksum on each of their emails and request the service for a spam likelihood.<ref>{{cite web | url=https://cwiki.apache.org/confluence/display/spamassassin/iXhash | title=IXhash | publisher=Apache | access-date=7 January 2020 | archive-date=31 August 2020 | archive-url=https://web.archive.org/web/20200831125801/https://cwiki.apache.org/confluence/display/spamassassin/iXhash | url-status=live }}</ref>