IRIX: Look in ftp://sgigate.sgi.com/Security/ and at
  http://www.sgi.com/support/security/index.html for SGI security
  advisories and patches.  SGI also runs a mailing list called
  "wiretap" for dissemination of IRIX security advisories from SGI;
  its subscription address is <wiretap-request@sgi.com>.  An article in 
  the Jul/Aug 1994 Pipeline discusses general Unix security with some
  IRIX-specific aspects.

  Unix in general: Look in ftp://ftp.cert.org/,
  ftp://ciac.llnl.gov/pub/ciac/ and http://www.8lgm.org/ for CERT, CIAC
  and 8lgm material (respectively) and general security information and
  tools.  If you have a lot of spare time, consider the
  comp.security.unix newsgroup and/or the bugtraq mailing list 
  (listproc@netspace.org, archived at http://www.securityfocus.com/)