Hiding in Plain Sight

Which Post-It note contains the correct password?

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Using Exchange 2007 Header Firewall

Each time an SMTP email is passed from one server to another, the receiving server records the hand-off in the SMTP headers of the email. This is usually recorded like this:

Received: from ex01.companyabc.com (10.12.1.81) by edge.companyabc.com (12.5.1.168) with Microsoft SMTP Server id 8.1.278.0; Fri, 20 Jun 2008 15:17:46 -0700

Customers often do not like their internal email infrastructure exposed in the SMTP headers for security reasons. It displays private information, such as internal IP addresses and SMTP versions that can be used by bad guys for targeted attacks. In the example above, SMTP Server id 8.1.278.0 tells me that edge.companyabc.com at public IP 12.5.1.168 is running Exchange Server 2007 SP1.

You can remove this information from the SMTP headers on Exchange 2007 using a concept called Header Firewall. This is done using the remove-adpermission cmdlet in the Exchange Management Shell. If you use Exchange 2007 Edge server(s), run the following one-liner:

Remove-ADPermission -id "EdgeSync - companyabc to Internet" -User "MS Exchange\Edge Transport Servers" -ExtendedRights Ms-Exch-Send-Headers-Routing

Note: Replace "EdgeSync - companyabc to Internet" with the name of the Internet bound send connector. You can run the Get-SendConnector cmdlet to display the names of all the Exchange send connectors.

For Exchange 2007 implementations that do not use Edge servers, use the following:

Remove-ADPermission -id "companyabc to Internet" -User "NT Authority\Anonymous Logon" -ExtendedRights Ms-Exch-Send-Headers-Routing

Again, replace "companyabc to Internet" with the name of the Internet bound send connector.

Essentially, you want to remove the rights of the last user account that will handle the outbound SMTP from reading the Ms-Exch-Send-Headers-Routing attribute in Active Directory. For Edge servers that will be the MS Exchange\Edge Transport Servers user account and for everything else it will be NT Authority\Anonymous Logon. Doing so will remove all the internal relay entries in the header before the last Exchange server, making the email appear like it originated from that last server.

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Pre-Conference Session with Marcus Murray

Monday I attended the pre-con session, "Step-By-Step Guide to Hack-Proofing Your Microsoft Network" by Marcus Murray. Marcus is a security rock star! Very funny and engaging.

Last year he scared the hell out of me when he demonstrated how easy it is to compromise a system and domain. Since then, I've unplugged the network cables from all my servers as a security precaution, but I'm sure that would only slow him down a little.

The session was very good, but it was a little slower paced than I was expecting and hoping for. The basic security concept is "you can't fix stupid." If the users have elevated rights (by that, I mean running with more permissions than they need to have to do their work) it's very easy to compromise their machine and use it as a springboard to the rest of the network.

The takeaway is this: You must kill your users. Kill zem all.

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New Certifications

May 2008 was a busy month for me.

In addition to writing a book, I passed five exams in the first three weeks and earned my MCITP:Enterprise Messaging Administrator (the premier Exchange 2007 administrator certification) and three MCTS certifications (SCOM 2007, ForeFront and Exchange 2007).

That makes 34 exams in a row that I've passed without failing, including my CISSP. Yes!! The streak remains unbroken!

I've put together a certifications page that lists the current certifications that I hold, which I'm rather proud of.

Tomorrow I'm off to TechEd and I can't wait! I'll be blogging at least once a day while I'm there. Check my blog all week. If you're going to TechEd yourself, I might meet you at the TechEd Blogger Ultra Lounge. See you there!

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Automatically Reset the FTP Service in Windows Server 2008

One of the more popular tips I've posted is, "How to automatically reset the FTP service," in Windows Server 2003. This tip is useful for public FTP sites where bad guys are trying to hack in, usually using a dictionary attack.

Doing the same thing in Windows Server 2008 is slightly different and has an important caveat - It will not work with the Microsoft FTP Publishing Service for IIS 7.0 yet. It will work fine if you use the standard FTP Publishing Service, included on the Windows Server 2008 DVD.

As in my original post, create a batch file named C:\Scripts\ResetFTPService.bat, as follows:

net stop msftpsvc
ping -n 10 127.0.0.1
net start msftpsvc

The batch file stops the FTP service, pings the loopback adapter 10 times to create a 10 second pause, and starts the FTP service again. Stopping the FTP service causes the hacker's session to be dropped immediately. Since no one can connect for 10 seconds, this creates a form of "tarpitting", making it too expensive to continue the attack.

To make the script run automatically on the correct event, use the Windows Server 2008 Task Manager:

• Right-click Task Manager (under Configuration in Server Manager) and select Create a Basic Task


• Name the task, "Reset FTP Service" and click Next


• Choose When a specific event is logged as the Task Trigger, click Next


• Select Log: System, Source: IIS-FTP, and Event ID: 100. Click Next


• Select Start a program and click Next


• Enter C:\Scripts\ResetFTPService.bat for the Program/script and click Next


• Click the checkbox for Open the Properties dialog for this task when I click Finish and then click Finish


• In the Properties window select Run whether user is logged on or not and Run with highest privileges


• Click OK


• Enter the User name and Password for running this task

This causes the ResetFTPService.bat batch file to run whenever an event ID 100 with source IIS-FTP is logged in the System event log.

Remember, this will not work with the Microsoft FTP Publishing Service for IIS 7.0 because this service strangely does not log failed logon attempts to the event log. I've posted a request to the IIS7 team for this functionality.

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New File Extensions Blocked in Outlook 2003 SP3

After several months of testing, a client recently deployed Service Pack 3 for Microsoft Office 2003 to nearly 10,000 clients via WSUS. They have a scripted routine that they follow during testing of patches and updates to ensure that there are no interoperability issues, but of course, you can't test everything. I mean, how are you going to know that a certain update will prevent an HP 4200 printer from feeding from the secondary paper tray? And yes, I've actually seen that happen.

Well, shortly after deployment they start getting complaints that emails with links to Public Folders (XNK files) can't be opened on Outlook 2003. Could it be that Microsoft actually did this on purpose? After an hour or so of re-reading all the scattered documentation for Office SP3, including Information about certain file types that are blocked after you install Office 2003 Service Pack 3 and the Downloadable list of issues that the service pack fixes, I couldn't find anything that documented this change.

I opened a case with Microsoft and found that not only are XNK extenstions blocked, but several others are as well. Here's an unofficial list of the extensions blocked by Outlook 2003 SP3 (I apologize for all the blank space that Blogger inserts before this table, please scroll down):

File Extension	File Type
.ade	Access Project Extension (Microsoft)
.adp	Access Project (Microsoft)
.app	Executable Application
.asp	Active Server Page
.bas	BASIC Source Code
.bat	Batch Processing
.cer	Internet Security Certificate File
.chm	Compiled HTML Help
.cmd	DOS CP/M Command File, Command File for Windows NT
.com	Command
.cpl	Windows Control Panel Extension (Microsoft)
.crt	Certificate File
.csh	csh Script
.der	DER Encoded X509 Certificate File
.exe	Executable File
.fxp	FoxPro Compiled Source (Microsoft)
.gadget	Windows Vista gadget
.hlp	Windows Help File
.hta	Hypertext Application
.inf	Information or Setup File
.ins	IIS Internet Communications Settings (Microsoft)
.isp	IIS Internet Service Provider Settings (Microsoft)
.its	Internet Document Set, Internet Translation
.js	JavaScript Source Code
.jse	JScript Encoded Script File
.ksh	UNIX Shell Script
.lnk	Windows Shortcut File
.mad	Access Module Shortcut (Microsoft)
.maf	Access (Microsoft)
.mag	Access Diagram Shortcut (Microsoft)
.mam	Access Macro Shortcut (Microsoft)
.maq	Access Query Shortcut (Microsoft)
.mar	Access Report Shortcut (Microsoft)
.mas	Access Stored Procedures (Microsoft)
.mat	Access Table Shortcut (Microsoft)
.mau	Media Attachment Unit
.mav	Access View Shortcut (Microsoft)
.maw	Access Data Access Page (Microsoft)
.mda	Access Add-in (Microsoft), MDA Access 2 Workgroup (Microsoft)
.mdb	Access Application (Microsoft), MDB Access Database (Microsoft)
.mde	Access MDE Database File (Microsoft)
.mdt	Access Add-in Data (Microsoft)
.mdw	Access Workgroup Information (Microsoft)
.mdz	Access Wizard Template (Microsoft)
.msc	Microsoft Management Console Snap-in Control File (Microsoft)
.msh	Microsoft Shell
.msh1	Microsoft Shell
.msh2	Microsoft Shell
.mshxml	Microsoft Shell
.msh1xml	Microsoft Shell
.msh2xml	Microsoft Shell
.msi	Windows Installer File (Microsoft)
.msp	Windows Installer Update
.mst	Windows SDK Setup Transform Script
.ops	Office Profile Settings File
.pcd	Visual Test (Microsoft)
.pif	Windows Program Information File (Microsoft)
.plg	Developer Studio Build Log
.prf	Windows System File
.prg	Program File
.pst	MS Exchange Address Book File, Outlook Personal Folder File (Microsoft)
.reg	Registration Information/Key for W95/98, Registry Data File
.scf	Windows Explorer Command
.scr	Windows Screen Saver
.sct	Windows Script Component, Foxpro Screen (Microsoft)
.shb	Windows Shortcut into a Document
.shs	Shell Scrap Object File
.ps1	Windows PowerShell
.ps1xml	Windows PowerShell
.ps2	Windows PowerShell
.ps2xml	Windows PowerShell
.psc1	Windows PowerShell
.psc2	Windows PowerShell
.tmp	Temporary File/Folder
.url	Internet Location
.vb	VBScript File or Any VisualBasic Source
.vbe	VBScript Encoded Script File
.vbs	VBScript Script File, Visual Basic for Applications Script
.vsmacros	Visual Studio .NET Binary-based Macro Project (Microsoft)
.vsw	Visio Workspace File (Microsoft)
.ws	Windows Script File
.wsc	Windows Script Component
.wsf	Windows Script File
.wsh	Windows Script Host Settings File
.xnk	Exchange Public Folder Shortcut

Nothing p$%#es me off more than undocumented changes in functionality. At this point in time, this information is not documented ANYWHERE on Microsoft's website.

I certainly don't mind Microsoft fixing security holes, but for crying out loud, DOCUMENT IT!!! How do they expect us to roll out critical patches and updates if they change functionality and don't tell anyone? No one looks good when that happens.

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TechEd 2008 Registration is Open!

TechEd 2008, the premier Microsoft IT learning experience, opened today for registration. I signed up as soon as the website came live. As you may know, TechEd is divided up into two separate events this year, Tech·Ed U.S. Developers (June 3-6, 2008) and Tech·Ed U.S. IT Professionals (June 10-13, 2008).

I'm thrilled to see that Marcus Murray is presenting a pre-conference seminar, "A Step-By-Step Guide to Hack-Proofing Your Microsoft Network." I wrote about Marcus at last year's TechEd, where he scared the living bejezus out of everyone in packed conference rooms. I can't wait to see what he's going to show off this year. I've removed the NIC from all my servers just to be safe. :)

As Brian Marble reported, TechEd 2008 will also be one of Bill Gates last public speaking engagements before he retires from Microsoft and embarks on his full time gig of giving money away. Bill and Melinda's philanthropy astounds me and warms my soul.

I'll be attending the Tech·Ed U.S. IT Professionals session. Let me know if you'll be going, too!

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