We have recently found ourself used as mail relays and put into the ORBS mail relay blocking system due to a bug in early anti-relay rulesets as used in both our local rules and RedHat 5.0, 5.1 and 5.2 (even though we never touch RedHat on serious servers, somehow our home-brew rulesets ended up bug-compatible). It seems that some spammers out there have discovered the power of: RCPT TO: <"targetat_private"@relay.host.name> where relay.host.name is obtained by reverse DNS lookup. Users of sendmail 8.9.x of course have no problem, neither do those who have updated their mail relay prevention rulesets recently, but I think there are enough RedHat 5.0, 5.1 and 5.2 users who are unaware of the problem to make it worth sending this out. I have put out a quick little script which fixes this. The script can be found at: ftp://typhaon.ucs.uwa.edu.au/pub/strobe-classb/RH5.0-5.2-patchscript This problem is checked for by my latest relay scanner at: ftp://typhaon.ucs.uwa.edu.au/pub/strobe-classb/strobe-classb-v1.8.tgz (some additional information about open relays and some problems they present can be found at http://typhaon.ucs.uwa.edu.au/presentations.html under 'E-mail Security', but hopefully everyone is well-informed of the issues by now; that paper is quite dated even if it is under a year old) David.
This archive was generated by hypermail 2b30 : Fri Apr 13 2001 - 14:52:30 PDT