squid helpers

Что такое helpers? При установке squid, есть опции как: --enable-basic-auth-helpers=\"list of helpers\" helpers to build and install as part of the normal helpers see the helpers/basic_auth directory. --enable-ntlm-auth-helpers=\"list of helpers\" This option selects which proxy_auth ntlm helpers process. For a list of available helpers see the helpers/ntlm_auth directory. --enable-negotiate-auth-helpers=\"list of helpers\" This option selects which proxy_auth negotiate helpers process. For a list of available helpers see the helpers/negotiate_auth directory. --enable-digest-auth-helpers=\"list of helpers\" helpers to build and install as part of the normal build process. For a list of available helpers see the helpers/digest_auth directory. --enable-external-acl-helpers=\"list of helpers\" This option selects which external_acl helpers to process. For a list of available helpers see the helpers/external_acl directory.