NNTPCache is Squid for news (plus lots more).

NNTPCache can take reader loads off major news-servers. Besides its
super efficient execution, a single or multi-layer concentric ring of
NNTPCaches can be arranged about one or more central news-servers on a
DNS round-robin basis. Such a wall of NNTPCaches provides drop-in
scalability, redundancy, authentication & security for even the
largest news-server heart. NNTPCache can transparently stitch multiple
split news-servers (e.g, one news-server carrying alt.binaries.*,
another carrying alt.*, and another carrying everything else) back
together, allowing news-server administrators to spread their news
feeds over multiple machines, or to out-source selected components.

NNTPCache minimizes the effects of news-server down time, by continuing
to provide cached news-data in the face of news-server fall-over.

NNTPCache natively supports a variety of AUTHINFO methods, including
/etc/passwd, generic unix pipes, LDAP and radius.