Translations:FAQ/272/en

Background
In UnrealIRCd 4.x there were 3 spamfilter types:
 * The simple spamfilter type supports only * and ?, allowing very fast matching.
 * The posix type uses regular expressions through the TRE regex engine. TRE has not been maintained for many years now, the last release is from 2009 and it is now a defunct product. It contains various bugs that will never be fixed, including bugs that may freeze the IRCd completely. The only reason it still exists in 4.x is that it can run the spamfilters that were used in UnrealIRCd 3.2.x.
 * The regex type uses regular expressions using the PCRE2 engine. This regex engine is used by various big projects, including PHP, and is a fully supported product.