securityassurance@microsoft.com - "Security Update for OS Microsoft Windows"

A malicious EXE file is doing the rounds, pretending to be an update from Microsoft and including some social engineering such as a fake PGP signature. The payload is an executable called KB960312.exe. Detection rates are poor, but it's clearly some hideous piece of malware that you really don't want anywhere near your PC.

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Subject: Security Update for OS Microsoft Windows
From: "Microsoft Official Update Center"

Dear Microsoft Customer,

Please notice that Microsoft company has recently issued a Security Update for OS
Microsoft Windows. The update applies to the following OS versions: Microsoft
Windows 98, Microsoft Windows 2000, Microsoft Windows Millenium, Microsoft Windows
XP, Microsoft Windows Vista.

Please notice, that present update applies to high-priority updates category. In
order to help protect your computer against security threats and performance
problems, we strongly recommend you to install this update.

Since public distribution of this Update through the official website
http://www.microsoft.com would have result in efficient creation of a malicious
software, we made a decision to issue an experimental private version of an update
for all Microsoft Windows OS users.

As your computer is set to receive notifications when new updates are available, you
have received this notice.

In order to start the update, please follow the step-by-step instruction:
1. Run the file, that you have received along with this message.
2. Carefully follow all the instructions you see on the screen.

If nothing changes after you have run the file, probably in the settings of your OS
you have an indication to run all the updates at a background routine. In that case,
at this point the upgrade of your OS will be finished.

We apologize for any inconvenience this back order may be causing you.


Thank you,

Steve Lipner
Director of Security Assurance
Microsoft Corp.


-----BEGIN PGP SIGNATURE-----
Version: PGP 7.1

3L0SDPQYESHKTVB7P898LE266163YL9LZQ6AU3LYK9JFM85HDX4S5FG0PEUY5HXP0
31Q8WAOREI4H0A7OF4UDTOG8HAXPAZMV91DI6B8XJEQ0636ND3XAWTCOOSNLIGHUN
ZSDHKKLZ099I6Y03BO91DGUTQMMFT0CWMCZQ4G0R0EYMNN199IEG0PKA6CE3ZPAB6
EJ4UN52NIIB4VF78224S7BCNFH3NP9V91T66QV0RKA2KOG0RA0EUM5VY17P41G016
I2YU34EL9XJQGS7C5GMDU4FJUIC3M3ZIAU6==
-----END PGP SIGNATURE-----

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Update: KB231660.exe has also been spotted with a different PGP signature, although securityassurance@microsoft.com remains the same. Also KB986008.exe, KB415282.exe, KB985274.exe, KB166277.exe .. probably a load more will be sent out over the next few hours.

Update 2: This has now been picked up by the folks at the ISC.