Distributed Checksum Clearinghouses. Overview The Distributed Checksum Clearinghouses or DCC is an anti-spam content filter that runs on a variety of operating systems. The counts can be used by SMTP servers and mail user agents to detect and reject or filter spam or unsolicited bulk mail. DCC servers exchange or "flood" common checksums. DSPAM Project Homepage. Nilsimsa. Kanji le nilsimsa sucta be lo notci gi'e karbi le sucta gi'e tolcri lo smigunma mu'i lonu fespu'i lo se maldustisna computes nilsimsa codes of messages and compares the codes and finds clusters of similar messages so as to trash spam A nilsimsa code is something like a hash, but unlike hashes, a small change in the message results in a small change in the nilsimsa code. Such a function is called a locality-sensitive hash.