|| Author: RadiatioN/EOF || Back to articles ||
Starting your app by viewing file properties
By some experiments i found a very interesting thing. Maybe you know the WinRAR or WinZIP explorer
extensions which attaches themself to the context menu of the windows explorer. So you maybe asked yourself
why is this fucking explorer so intelligent to decide whether this file is extractable or not?
Hehe the answer is simple: the explorer is stupid but the explorer extension is intelligent :)
I noticed that by clicking on a installation package from the internet to its context menu. i wanted to 
debug the file with ollydbg's context menu entry. i wondered why WinRAR was showing me a entry "Extract this
file..." on a EXE file!?!? I stopped debugging and went on seach how this could be. So here you now
can read how it works. First i thought, ok nice feature and then i fall back into my VX origin for starting
viral stuff :) 

four new important things have been born with this new technique:
- We are able about this extensions to start our viral stuff without any autorun entries anywhere.
- this would also work in secure mode of windows
- start your viral stuff just by showing file properties - a VXer dream comes true xD
- most of AV and autorun checking apps already don't know this method

i never implemented this in an app. you will have to do it yourself. i tested it with a test dll
giving me a messagebox on loading, it worked really well. at the end of the tutorial i will add a 
*.reg file for you, so its easier for you to implement it. This technique seems more complex then it 
really is!

ok enough intruduction, let me explain how this works. We need to change the windows registry on 
some places. also we need a dll which will be loaded on viewing the properties. this dll must!!! be 
dropped on harddisk or it will not work. you could move it to windows or system32 directory for example. 
If you have infected the PC by exe you could go this way (for explanation look under it):

 | EXE infects PC                      |
 | EXE dropps DLL                      |
 | EXE creates mutex                   |
 | EXE writes to registry              |
 | DLL loads                           |
 | DLL does nothing cause mutex exists |
 | PC reboots |     (Workflow goes from up to down)
 | Windows explorer loads                      |
 | explorer loads extension for *.lnk files    |
 | DLL loads                                   |
 | DLL loads EXE file cause mutex doesnt exist |
 | EXE creates mutex                           |

ok as i already said you must infect the PC, how you do it is your problem :) ok, then the app should 
drop a dll onto harddisk, where is not important but it must keep at that place. Then the app should create 
a mutex so the dll can decide whether the app is already started or not. You must do this because the dll
gets often loaded and unloaded, everytime the explorer checks properties of our file. Which file this is,
is the next step to set in registry. its described in the next chapter! the best way to start the dll
is to register it for the *.lnk file extension. This extension will be not shown to the user and is found
very often on a normal computer. Just open start menu and dll + app will be loaded :P

But what happens if the computer reboots?
The Windows explorer will be loaded as normal. So if there is any link on the desktop the explorer 
extension dll will be loaded by the explorer automatically. For now the DLL has to start the app if 
the mutex is not already created. At the app startup we have to create the mutex to avoid double starting.
the app can run now as an normal virus.

Installing explorer extension in registry
1. We have to create a new key like: (replace [NAME] with anything you want)

2. Set default value of this key to a non-existing CLSID. syntax must be the same!
(you can generate it randomly with hex characters)

3. Create a new Key like: (CLSID must be the same as above)

4. Set default value of this key to path of your dll

5. create an entry under
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved
(Name of value also the CLSID)

6. set its value to

all values are REG_SZ (string terminated with zero)

*.REG Files
As an example, here a reg file with my test settings. Just copy/paste it in a *.reg file.

----- FILE START -----
Windows Registry Editor Version 5.00



[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Shell Extensions\Approved]

------ FILE END ------

If you don't want to crash the system, your dll should not longer need than some milliseconds in main().
Cause if your dll needs to much time, the explorer is waiting until your dll comes back from main() 
function. beware of this, its important!

If your dll loads not instantly you add the entries to registry, wait some time ... it will be loaded
always, be sure. Windows seems to call this dll like in a timer, but the time is not really defined ;)

Now you should be able to write a code to start your malware, virus worm and so on without using
public known startup methods :) 

Last words
Some nice greetings go to the complete EOF group and especially to Skyout my good friend *keep on rocking*

As always no copyright - free for any use

Tutorial written by RadiatioN in May 2006 at EOF group

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