Hashbusters

A hashbuster, in computer science, is data inserted with the intent of causing different hash sums to be produced for nearly identical content. i.e. "busting" hash sums.

For example, spammers who send massive quantities of the same message may be caught by programs using hash functions or checksums to respond to an overabundance of identical emails. To evade this defense, spammers often use a hashbusting technique to corrupt the checksums.