a) Email as an attachment of MIME audio/x-wav type.
enabled and using a version of IE vulnerable to the exploits
discussed in MS01-020 (e.g. IE 5.0 or IE 5.01 without SP2).
c) Machine to machine in the form of IIS attacks (primarily
attempting to exploit vulnerabilities created by the effects of Code
Red II, but also vulnerabilities previously patched by MS00-078)
d) Highlighting either a .eml or .nws in Explorer with Active Desktop
enabled (W2K/ME/W98 by default) then the THUMBVW.DLL will execute the
file and attempt to download the README.EXE referenced in it
(depending on your IE version and zone settings).
e) Mapped drives. Any infected machine which has mapped network
drives will likely infect all of the files on the mapped drive and
To prevent yourself from being infected;
a) Ensure all IE versions have applied MS01-027 (or are IE 5.01SP2 or
b) Disable Active Scripting in IE
c) Ensure all IIS installations have applied MS01-044 (or at the very
d) Use the CALCS program to modify the permissions on TFTP.EXE to
remove all use;
CALCS %systemroot%/system32/tftp.exe /D Everyone
CALCS %systemroot%/system32/tftp.exe /D System
Do the same for CMD.EXE
(note, this could be tried with THUMBVM.DLL as well, haven't tried
this myself yet)
e) Ensure that TFTP is not permitted out through your network gateway
(note that newly infected machines may try and TFTP *internally* from
some other infected machine you have on your network)
f) Modify or remove;
Nimda is viral, so while you can remove various files that it drops
it probably will not be cleaned completely by manual means. This
means you will have to use your AntiVirus vendor's product to
a) Load.exe dropped as hidden/system file (probably in %systemroot%)
b) Riched20.dll dropped with today's date as hidden/system file.
c) Readme.exe dropped in every directory
d) Admin.dll dropped in /scripts and/or root directories (not the
_vti_bin directories of FrontPage)
e) .eml and .nws files dropped in every directory
f) Possibly modified your default home page in web dirs.
g) Infected numerous files (if not all files) with the 56kb
h) Reports of people having files lumped together into .eml files
Check with your AV Vendor regularly for updates to the cleansing
programs. I would appreciate any reports from AV Vendors as to how
complete they feel their cleaners currently are. I will do an update
later tonight based on responses.
Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor