[Full-Disclosure] RE: Probable new MS DCOM RPC worm for Windows

["Carey, Steve T GARRISON" <steven-carey@xxxxxxxxxxx>]

We have seen a number of infections of Nachi/Welchia on patched systems.  Was
told that the MS03-026 patch was only 60% effective, so you still had a 1 in 3
chance of being infected.  Apparently the MS03-039 patch fixes the entire
vulnerability and not just some of it.  We re-enforced the rule for keeping the
anti-virus current, which stopped Nachi/Welchia worm (in most cases, not all).

Steve Carey

-----Original Message-----
From: Derek Vadala [mailto:derek@xxxxxxxxxxxx]
Sent: Thursday, September 25, 2003 2:44 PM
To: pauls@xxxxxxxxxxxx
Cc: full-disclosure@xxxxxxxxxxxxxxxx; incidents@xxxxxxxxxxxxxxxxx
Subject: RE: Probable new MS DCOM RPC worm for Windows


> I'm thinking that there *has* to be a variant of Nachi/Welchia in the
> wild.  We have machines that were patched for MS03-026 (verified by
> scanning with multiple scanners) but not patched for MS03-039 (ditto)
> and they have been infected by something that triggers my Nachi rule in
> snort.  This should *not* be possible with the "original" Nachi/Welchia,
> so my assumption is that either something new has been released or the
> worm has mutated somehow.
>
> Mind you, this is anecdotal and a very small incidence (only three
> machines so far), but it still bears watching IMHO.  I've been surprised
> to not see any discussion on the lists about a new variant.  Perhaps no
> one is looking?
>
> Paul Schmehl (pauls@xxxxxxxxxxxx)

We've seen the same thing over here. I've had a handful of machines
(perhaps 15-20 out of 2500) here that were reported to be patched against
MS03-026 yet became infected with Welchia. These machines were not patched
against MS03-039. One possibility is that the systems were already
infected with Welchia at the time they were patched against MS03-026.

I know of at least one or two cases here where the technical support
person assigned to fix a particular system didn't appropriately follow the
removal procedures and left a patched, but infected, system. I have to
assume this is happening without notice in other cases, since there
haven't been reports of a variant, and the number of systems in this
situation is rather low.

So I'm betting user error, though I find it hard to believe there isn't
another variant making the rounds.





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