荔园在线
荔园之美,在春之萌芽,在夏之绽放,在秋之收获,在冬之沉淀
[回到开始]
[上一篇][下一篇]
发信人: netlife (灌醉自己), 信区: Newsoftware
标 题: 新病毒(ZZ)
发信站: 荔园晨风BBS站 (Thu Sep 20 07:49:59 2001), 转信
寄信人: peach (呆呆)
标 题: 新病毒
发信站: BBS 水木清华站 (Wed Sep 19 14:19:22 2001)
来 源: 166.111.172.127
【 以下文字转载自 peach 的信箱 】
寄信人: monsieur (沧海横流)
标 题: 没主题
发信站: BBS 水木清华站 (Wed Sep 19 14:15:17 2001)
来 源: 202.112.50.8
CERT Advisory CA-2001-26 Nimda Worm
Original release date: September 18, 2001
Source: CERT/CC
A complete revision history is at the end of this file.
Systems Affected
* Systems running Microsoft Windows 95, 98, ME, NT, and 2000
* Systems running Microsoft Windows 95, 98, ME, NT, and 2000
Overview
The CERT/CC has received reports of new malicious code known as
the
"W32/Nimda worm" or the "Concept Virus (CV) v.5." This new
worm
appears to spread by multiple mechanisms:
* from client to client via email
* from client to client via open network shares
* from web server to client via browsing of compromised web sites
* from client to web server via active scanning for and
exploitation
of the "Microsoft IIS 4.0 / 5.0 directory traversal"
vulnerability
(VU #111677)
* from client to web server via scanning for the back doors
left
* from client to web server via scanning for the back doors
left
behind by the "Code Red II" (IN-2001-09), and
"sadmind/IIS"
(CA-2001-11) worms
Initial analysis indicates that the worm contains no
destructive
payload beyond modification of web content to facilitate its
own
propagation.
We are also receiving reports of denial of service as a result
of
network scanning and email propagation.
I. Description
The Nimda worm has the potential to affect both user
workstations
(clients) running Windows 95, 98, ME, NT, or 2000 and servers
running
Windows NT and 2000.
Email Propagation
This worm propagates through email arriving as a
MIME
"multipart/alternative" message consisting of two sections. The
first
section is defined as MIME type "text/html", but it contains no
text,
so the email appears to have no content. The second section is
defined
as MIME type "audio/x-wav", but it contains a
base64-encoded
attachment named "readme.exe", which is a binary executable.
Due to a vulnerability described in CA-2001-06 (Automatic Execution
of
Embedded MIME Types), any mail software running on an x86
platform
that uses Microsoft Internet Explorer 5.5 SP1 or earlier (except
IE
5.01 SP2) to render the HTML mail automatically runs the
enclosed
attachment and, as result, infects the machine with the worm. Thus,
in
vulnerable configurations, the worm payload will automatically
be
triggered by simply opening (or previewing) this mail message. As
an
executable binary, the payload can also be triggered by simply
running
the attachment.
the attachment.
The email message delivering the Nimda worm appears to also have
the
following characteristics:
* The text in the subject line of the mail message appears to
be
variable, but those seen to date have been over 80
characters
long.
* There appear to be many slight variations in the attach
binary
file, causing the MD5 checksum to be different when one
compares
different attachments from different email messages. However,
the
file length of the attachment appears to consistently be
57344
bytes.
Payload
Infected client machines attempt to send copies of the Nimda worm
via
email to all addresses found in the Windows address book.
Likewise, the client machines begin scanning for vulnerable
IIS
servers. Nimda looks for backdoors left by previous IIS worms:
Code
Red II [IN-2001-09] and sadmind/IIS worm [CA-2001-11]. It
also
attempts to exploit the IIS Directory Traversal vulnerability
(VU
#111677). The selection of potential target IP addresses follows
these
rough probabilities:
* 50% of the time, an address with the same first two octets will
be
chosen
* 25% of the time, an address with the same first octet will
be
chosen
* 25% of the time, a random address will be chosen
The infected client machine transfers a copy of the Nimda code to
any
server that it scans and finds to be vulnerable. Once running on
the
server machine, the worm traverses each directory in the
system
(including all those accessible through a file shares) and
write a
copy of itself to disk using the name "README.EML". When a
directory
containing web content (e.g., HTML or ASP files) is found,
the
following snippet of Javascript code is appended to every one of
these
web-related files:
<DEFANGED_script language="JavaScript">
window.open("readme.eml", null, "resizable=no,top=6000,left=6000")
</script>
This modification of web content allows further propagation of
the
worm to new clients through a browser or browsing of a network
file
system.
Browser Propagation
As part of the infection process, the Nimda worm modifies all
web
content files it finds (including, but not limited to, files
with
.htm, .html, and .asp extensions). As a result, any user browsing
web
content on the system, whether via the file system or via a
web
server, may download a copy of the worm. Some browsers
may
automatically execute the downloaded copy, thereby infecting
the
browsing system.
File System Propagation
The Nimda worm creates numerous copies of itself (using the
name
README.EML) in all writable directories (including those found
on a
network share) to which the user has access. If a user on
another
system subsequently selects the copy of the worm file on the
shared
network drive in Windows Explorer with the preview option enabled,
the
network drive in Windows Explorer with the preview option enabled,
the
worm may be able to compromise that system.
System FootPrint
The scanning activity of the Nimda worm produces the following
log
entries for any web server listing on port 80/tcp:
GET /scripts/root.exe?/c+dir
GET /MSADC/root.exe?/c+dir
GET /c/winnt/system32/cmd.exe?/c+dir
GET /d/winnt/system32/cmd.exe?/c+dir
GET /scripts/..%5c../winnt/system32/cmd.exe?/c+dir
GET /_vti_bin/..%5c../..%5c../..%5c../winnt/system32/cmd.exe?/c+dir
GET /_mem_bin/..%5c../..%5c../..%5c../winnt/system32/cmd.exe?/c+dir
GET
/msadc/..%5c../..%5c../..%5c/..\xc1\x1c../..\xc1\x1c../..\xc1\x1c..
/winnt/system
32/cmd.exe?/c+dir
GET /scripts/..\xc1\x1c../winnt/system32/cmd.exe?/c+dir
GET /scripts/..\xc0/../winnt/system32/cmd.exe?/c+dir
GET /scripts/..\xc0\xaf../winnt/system32/cmd.exe?/c+dir
GET /scripts/..\xc1\x9c../winnt/system32/cmd.exe?/c+dir
GET /scripts/..%35c../winnt/system32/cmd.exe?/c+dir
GET /scripts/..%35c../winnt/system32/cmd.exe?/c+dir
GET /scripts/..%5c../winnt/system32/cmd.exe?/c+dir
GET /scripts/..%2f../winnt/system32/cmd.exe?/c+dir
Note: The first four entries in these sample logs denote attempts
to
connect to the backdoor left by Code Red II, while the remaining
log
entries are examples of exploit attempts for the Directory
Traversal
vulnerability.
II. Impact
Intruders can execute arbitrary commands within the
LocalSystem
security context on machines running the unpatched versions of
IIS.
Host that have been compromised are also at high risk for being
party
to attacks on other Internet sites.
The high scanning rate of the Nimda worm may also cause
bandwidth
denial-of-service conditions on networks with infected machines.
III. Solutions
Recommendations for System Administrators of IIS machines
To determine if your system has been compromised, look for
the
following:
* root.exe artifact (indicates a compromise by Code Red II
or
sadmind/IIS worms making the system vulnerable to the Nimda
worm)
* admin.dll artifact or unexpected .eml files in the
directories
with web content (indicates compromise by the Nimda worm)
The only safe way to recover from the system compromise is to
format
the system drive(s) and reinstall the system software from
trusted
media (such as vendor-supplied CD-ROM). Additionally, after
the
software is reinstalled, all vendor-supplied security patches must
be
applied. The recommended time to do this is while the system is
not
connected to any network. However, if sufficient care is taken
to
disable all server network services, then the patches can
be
downloaded from the Internet.
Detailed instructions for recovering your system can be found in
the
CERT/CC tech tip:
Steps for Recovering from a UNIX or NT System Compromise
http://www.cert.org/tech_tips/win-UNIX-system_compromise.
html
Steps for Recovering from a UNIX or NT System Compromise
http://www.cert.org/tech_tips/win-UNIX-system_compromise.
html
Apply the appropriate patch from your vendor
A cumulative patch which addresses all of the
IIS-related
vulnerabilities exploited by the Nimda worm is available
from
Microsoft at
http://www.microsoft.com/technet/security/bulletin/MS01-044.
asp
Recommendations for End User Systems
Apply the appropriate patch from your vendor
If you are running a vulnerable version of Internet Explorer (IE),
the
CERT/CC recommends applying patch for the "Automatic Execution
of
Embedded MIME Types" vulnerability available from Microsoft at
http://www.microsoft.com/technet/security/bulletin/MS01-020.
asp
Run and Maintain an Anti-Virus Product
It is important for users to update their anti-virus software.
Most
anti-virus software vendors have released updated information,
tools,
or virus databases to help detect and partially recover from
this
malicious code. A list of vendor-specific anti-virus information
can
be found in Appendix A.
Many anti-virus packages support automatic updates of
virus
definitions. We recommend using these automatic updates
when
available.
Don't open e-mail attachments
The Nimda worm may arrive as an email attachment named "readme.
exe".
Users should not open this attachment.
Disable JavaScript End-user systems can become infected with
the
Nimda worm by browsing web sites hosted by infected servers.
This
method of infection requires the use of JavaScript to be
successful.
Therefore, the CERT/CC recommends that end user systems
disable
JavaScript.
Appendix A. Vendor Information
Antivirus Vendor Information
Central Command, Inc.
http://support.centralcommand.com/cgi-bin/command.
cfg/php/endus
er/std_adp.php?p_refno=010918-000005
Command Software Systems
http://www.commandsoftware.com/virus/nimda.html
Data Fellows Corp
http://www.datafellows.com/v-descs/nimda.shtml
McAfee
http://vil.mcafee.com/dispVirus.asp?virus_k=99209&
Sophos
http://www.sophos.com/virusinfo/analyses/w32nimdaa.html
Symantec
http://www.symantec.com/avcenter/venc/data/w32.nimda.a@mm.
html
Trend Micro
http://www.antivirus.com/vinfo/virusencyclo/default5.
asp?VName=
TROJ_NIMDA.A
http://www.antivirus.
com/pc-cillin/vinfo/virusencyclo/default5.
asp?VName=TROJ_NIMDA.A
You may wish to visit the CERT/CC's computer virus resources
page
located at
http://www.cert.org/other_sources/viruses.html
--
Wellcome to http://192.168.48.13
Wellcome to ftp://192.168.48.13
提供光盘刻录服务
-----------------------------------------------
数据光盘 音乐光盘 视频光盘 光盘复制
*[=M☆别人笑我太疯颠,我笑他人看不穿☆*[=S
※ 来源:·荔园晨风BBS站 bbs.szu.edu.cn·[FROM: 192.168.48.13]
[回到开始]
[上一篇][下一篇]
荔园在线首页 友情链接:深圳大学 深大招生 荔园晨风BBS S-Term软件 网络书店