Archive for category Security

DJBDNS security patch


If the administrator of publishes the DNS data
through tinydns and axfrdns, and includes data for
transferred from an untrusted third party, then that third party can
control cache entries for, not just This is
the result of a bug in djbdns pointed out by Matthew Dempsky. (In short,
axfrdns compresses some outgoing DNS packets incorrectly.)

Even though this bug affects very few users, it is a violation of the
expected security policy in a reasonable situation, so it is a security
hole in djbdns. Third-party DNS service is discouraged in the djbdns
documentation but is nevertheless supported. Dempsky is hereby awarded

The next release of djbdns will be backed by a new security guarantee.
In the meantime, if any users are in the situation described above,
those users are advised to apply Dempsky's patch and requested to accept
my apologies. The patch is also recommended for other users; it corrects
the bug without any side effects. A copy of the patch appears below.

---D. J. Bernstein 
   Research Professor, Computer Science, University of Illinois at Chicago

--- response.c.orig     2009-02-24 21:04:06.000000000 -0800
+++ response.c  2009-02-24 21:04:25.000000000 -0800
@@ -34,7 +34,7 @@
         uint16_pack_big(buf,49152 + name_ptr[i]);
         return response_addbytes(buf,2);
-    if (dlen <= 128)
+    if ((dlen <= 128) && (response_len < 16384))
       if (name_num < NAMES) {
        name_ptr[name_num] = response_len;

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Nmap 4.85BETA7 Released to Scan for Conficker Worm

The Conficker worm is receiving a lot of attention because of its vast scale (millions of machines infected) and advanced update mechanisms. Conficker isn’t the end of the Internet (despite some of that hype), but it is a huge nuisance we can all help to clean up.

Thanks to excellent research by Tillmann Werner and Felix Leder of The Honeynet Project and implementation work by Ron Bowes, David Fifield, Brandon Enright, and Fyodor, we’ve rolled out a new Nmap release which can remotely scan for and detect infected machines. Nmap 4.85BETA7 is now available from the download page, including official binaries for Windows and Mac OS X. To scan for Conficker, use a command such as:

nmap -PN -T4 -p139,445 -n -v –script smb-check-vulns,smb-os-discovery –script-args safe=1 [targetnetworks]

You will only see Conficker-related output if either port 139 or 445 are open on a host. A clean machine reports at the bottom: “Conficker: Likely CLEAN”, while likely infected machines say: “Conficker: Likely INFECTED”. For more advice, see this nmap-dev post by Brandon Enright. Dan Kaminsky broke the story on

While Conficker gets all the attention, 4.85BETA7 also has many other great improvements.


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