[iwar] [fc:Details.on.the.worm]

From: Fred Cohen (fc@all.net)
Date: 2001-09-18 19:17:32


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From: Fred Cohen <fc@all.net>
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Date: Tue, 18 Sep 2001 19:17:32 -0700 (PDT)
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Subject: [iwar] [fc:Details.on.the.worm]
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Hey,

We have been receiving reports of a new worm from a large number of
users.  Instead of deluging BUGTRAQ with traffic more appropriate for
INCIDENTS, we are posting a summary of the worm and the vulnerabilities
it exploits:

A new worm named W32/Nimda-A (known aliases are Nimda, Minda, Concept V,
Code Rainbow) began to proliferate the morning of September 18, 2001 on
an extremely large scale that targets the Microsoft Windows platform. 
It attempts to spread via three mechanisms; as an email attachment, a
web defacement download, and through exploitation of known IIS
vulnerabilities.  Collateral damage include network performance
degradation due to high consumption of bandwidth during the propagation
process.  There have been reports of Apache Servers being inadvertantly
affected by Nimda by being subjected to a denial of service condition
(the configuration of these servers is not known). 

This worm takes advantage of multiple vulnerabilities and backdoors. 
The worm spreads via e-mail and the web.  Through the e-mail vector, the
worm arrives in the users inbox as a message with a variable subject
line.  The e-mail contains an attachment named 'readme.exe'.  This worm
formats the e-mail in such a way as to take advantage of a hole in older
versions of Internet Explorer.  Outlook mail clients use the Internet
Explorer libraries to display HTML e-mail, so by extension Outlook and
Outlook Express are vulnerable as well, if Internet Explorer is
vulnerable.  The hole allows the readme.exe program to execute
automatically as soon as the e-mail is previewed or read. 

Once it has infected a new victim, it mails copies of itself to other
potential victims, and begins scanning for vulnerable IIS Web servers. 
When scanning for vulnerable IIS servers, it attempts to exploit the
Unicode hole (bid 1806) and the escaped characters decoding command
execution vulnerability (bid 2708).  It also attempts to access the
system via the root.exe backdoor left by Code Red II.  Once it finds a
vulnerable IIS server, it installs itself in such a way that visitors to
the now-infected web site will be sent a copy of a .eml file, which is a
copy of the e-mail that gets sent.  If the victim is using Internet
Explorer as their browser, and they are vulnerable to the hole, they
will execute the readme.exe attachment in the same way as if they had
viewed an infected e-mail message. 

Attack Data:

Examination of the worm reveals the following attack strings used to
exploit IIS Web servers. 

'/scripts/..%255c..'
'/_vti_bin/..%255c../..%255c../..%255c..'
'/_mem_bin/..%255c../..%255c../..%255c..'
'/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%'
'/scripts/..%c1%1c..'
'/scripts/..%c0%2f..'
'/scripts/..%c0%af..'
'/scripts/..%c1%9c..'
'/scripts/..%%35%63..'
'/scripts/..%%35c..'
'/scripts/..%25%35%63..'
'/scripts/..%252f..'

To those strings are added /winnt/system32/cmd.exe?/c+dir

Other attacks include:

'/scripts/root.exe?/c+dir'
'/MSADC/root.exe?/c+dir'

It is believed that all of the vulnerabilities exploited by this worm
are known. 

The links below provide fix information.  Administrators and users are
advised to apply patches as soon as possible.  If further analysis
concludes that other vulnerabilities are involved, updated information
will be posted to the list. 

See:

Bugtraq ID: 2524 / CVE ID: CAN-2001-0154
Microsoft Security Bulletin MS01-020
<a href="http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS01-020.asp">http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS01-020.asp>
VulDB: http://www.securityfocus.com/bid/2524

Bugtraq ID: 2708 / CVE ID:  CAN-2001-0333
Microsoft Security Bulletin MS01-026
<a href="http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS01-026.asp">http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS01-026.asp>
VulDB: http://www.securityfocus.com/bid/2708

Bugtraq ID: 1806 / CVE ID:  CVE-2000-0884
Microsoft Security Bulletin MS00-078
<a href="http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS00-078.asp">http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS00-078.asp>
<a href="http://www.securityfocus.com/bid/1806">http://www.securityfocus.com/bid/1806>

Microsoft IIS Lockdown Tool:

<a href="http://www.microsoft.com/technet/treeview/default.asp?url=/technet/itsolutions/security/tools/locktool.asp">http://www.microsoft.com/technet/treeview/default.asp?url=/technet/itsolutions/security/tools/locktool.asp>

References:

Symantec W32.Nimda.A@mm
<a href="http://www.symantec.com/avcenter/venc/data/w32.nimda.a@mm.html">http://www.symantec.com/avcenter/venc/data/w32.nimda.a@mm.html>

McAfee W32/Nimda@MM
<a href="http://vil.nai.com/vil/virusSummary.asp?virus_k=99209">http://vil.nai.com/vil/virusSummary.asp?virus_k=99209>

Sophos W32/Nimda-A
<a href="http://www.sophos.com/virusinfo/analyses/w32nimdaa.html">http://www.sophos.com/virusinfo/analyses/w32nimdaa.html>

For discussion of infection or attack attempts, subscribe to the INCIDENTS
mailing list.  For discussion of the worm itself and others, FORENSICS and
FOCUS-VIRUS are more appropriate than BUGTRAQ.

---

Dave Ahmad
Security Focus
www.securityfocus.com

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