Microsoft office file block & MOICE

Published: 2008-05-13
Last Updated: 2008-05-13 23:23:11 UTC
by Swa Frantzen (Version: 1)
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Microsoft introduced the ability to block file formats to the different  programs in office and safer ways to open suspect files about a year ago.

The file blocking is not based on the file extension but on the actual format (so renaming a rich text file (.rtf) to a .doc won't get around the restriction). Unfortunately it's set by making changes in the registry and perhaps worse: it's a blocklist instead of a list of allowed file types. Still if you never intend to open e.g. rtf files, you could block it.

Microsoft Office Isolated Conversion Environment (MOICE) is an alternate way to open office files away from the actual tool. Use it instead of the real thing if you cannot resist opening that unsolicited attachment promising whatever it promises.

It seems these tools aren't widely used, hence drawing a bit more attention to them might help protect a few in the end.

Swa Frantzen -- Gorilla Security

Keywords: Microsoft
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May 2008 black tuesday overview

Published: 2008-05-13
Last Updated: 2008-05-13 22:01:08 UTC
by Swa Frantzen (Version: 1)
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Overview of the May 2008 Microsoft patches and their status.

# Affected Contra Indications Known Exploits Microsoft rating ISC rating(*)
clients servers
MS08-026 Multiple vulnerabilities allow code execution when opening a malicious file. Files opened with word and edited with word in outlook are of particular concern.
Replaces MS08-009.

KB 951207 No publicly known exploits Critical Critical Important
MS08-027 The fixed vulnerability is an input validation failure leading to memory corruption and code execution.
Replaces MS08-012 and MS07-037.

KB 951208
No publicly known exploits Critical Critical Important
MS08-028 The fixed vulnerability is an input validation failure leading to a buffer overflow and allowing code execution.
Jet database engine

KB 950749

SA 950627
Actively exploited Critical PATCH NOW Important

Microsoft onecare, antigen, defender and forefront use the malware protection engine. It suffers from multiple input validation failures leading to a Denial of Service.

Microsoft malware protection engine


KB 952044
No publicly known exploits Moderate Less Urgent Important


We will update issues on this page as they evolve.
We appreciate updates
US based customers can call Microsoft for free patch related support on 1-866-PCSAFETY
(*): ISC rating
  • We use 4 levels:
    • PATCH NOW: Typically used where we see immediate danger of exploitation. Typical environments will want to deploy these patches ASAP. Workarounds are typically not accepted by users or are not possible. This rating is often used when typical deployments make it vulnerable and exploits are being used or easy to obtain or make.
    • Critical: Anything that needs little to become "interesting" for the dark side. Best approach is to test and deploy ASAP. Workarounds can give more time to test.
    • Important: Things where more testing and other measures can help.
    • Less Urgent: Typically we expect the impact if left unpatched to be not that big a deal in the short term. Do not forget them however.
  • The difference between the client and server rating is based on how you use the affected machine. We take into account the typical client and server deployment in the usage of the machine and the common measures people typically have in place already. Measures we presume are simple best practices for servers such as not using outlook, MSIE, word etc. to do traditional office or leisure work.
  • The rating is not a risk analysis as such. It is a rating of importance of the vulnerability and the perceived or even predicted threat for affected systems. The rating does not account for the number of affected systems there are. It is for an affected system in a typical worst-case role.
  • Only the organization itself is in a position to do a full risk analysis involving the presence (or lack of) affected systems, the actually implemented measures, the impact on their operation and the value of the assets involved.
  • All patches released by a vendor are important enough to have a close look if you use the affected systems. There is little incentive for vendors to publicize patches that do not have some form of risk to them.

Swa Frantzen -- Gorilla Security

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OpenSSH: Predictable PRNG in debian and ubuntu Linux

Published: 2008-05-13
Last Updated: 2008-05-13 21:30:19 UTC
by Swa Frantzen (Version: 4)
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Debian and Ubuntu Linux users should look into their OpenSSH setup. It turns out the PRNG (Pseudo Random Number Generator) as used was predictable.

Remember patching isn't enough, you need to regenerate keys generated on these machines! Including those used in SSL certificates (X.509).

Worse: even good keys apparently can be exposed due to this. Quoting from the Debian reference below:

"Furthermore, all DSA keys ever used on affected Debian systems for signing or authentication purposes should be considered compromised; the Digital Signature Algorithm relies on a secret random value used during signature generation."

So merely using your (good) keys on an affected machine might be enough to get the key itself compromised.

Interested in what makes the PRNG be predictable I started reading the changelog and found this:

* Re-introducing seeding of the random number generator.  Patch from the

-- Florian Weimer <>  Thu, 08 May 2008 01:58:40 +0200

Guess that sums it up ...

Update: Alex dug deeper and found it might have been triggered by a tool to find use of uninitialized memory (valgrind) and bug report 363516

Update: Florian provided a link to a tool to detect these weak keys

Swa Frantzen -- Gorilla Security

Keywords: linux openssh
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