2

Is checking the state of the supporting files of the Windows registry hives enough to detect if a new software/malware has been installed on the computer or a given Windows regsitry key has been modified ?

By checking the state I mean verifying for example the last modification date, the size of the file and so on. It is something I can do with this Python function, for example.

It could be helpful to remember that the supporting files of the Windows registry hives are SAM, security, system, software, default and ntuser.

Maybe the best way to ask the question: what is the full ASEP list to survey for any eventual malware (or even legitimate software) installation ?

3

There are just too many ways in which malware can persist on a Windows machine without touching the registry. For example:

Windows Startup Folder
Although it is the most simple and obvious to be found, still I am describing it here just to show that this technique doesn't require touching the registry. In Windows family of operating systems every user has a particular statup folder in which any executable or shortcut file placed will be automatically executed by the operating system upon user login.

For Windows XP and Windows Server 2003, the starup folder path is:

C:\Documents and Settings\"User Name"\Start Menu\Programs\Startup

For Windows 7 and Windows 8, the path is:

C:\Users\<User Profile folder name>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup

If the malware is placed in the above locations, it will be executed every time the user is logged in and this technique doesn't require any modification to the Windows registry.

Trojanize Binaries
The malware can also infect pre-existing binaries and embed itself with the auto-executable executable files. For example, replacing uTorrent.exe with a trojanized uTorrent.exe in which the malware is embedded with the main executable results in execution of the legitimate program as well as execution of the malicious malware file and no mofification is required to be made to the registry (assuming that uTorrent.exe is in the auto-executable files list).

DLL Hijacking
Just placing the malware DLL file at a particular location can also result in the execution of the malicious DLL file. This attack is commonly known as the DLL Hijacking in which the malicious DLL file is placed in a location that is searched first by the OS before it gets to the legitimate DLL path. Again, no changes is required to the registry for executing the malicious DLL through DLL hijacking.

We haven't even touched the BIOS persistent malware even though those techniques have also been publicly demonstrated. In short, there are too many techniques and methods through which malware can be executed automatically at boot time. Once the attacker gets hold of the machine, it is usually futile to detect it at that point. The detection should then move to the network and outgoing traffic from the machine should be analyzed. Note however, that you cannot run netstat, wireshark or any other tool on the compromised machine as rootkits can hide itself from any tool running on the compromised machine. Therefore, keeping in view the concept of defense in depth, you should analyze and protect your assets from the identified threats at multiple locations and hope that not every location can be compromised at once by the attacker.

0

Writing entries to the Run subkey is the most common technique used by malware to launch itself automatically. The Autoruns tool shows you what programs are configured to run during system bootup or login. It lists executables that run, DLLs loaded into Internet Explorer and other programs, and drivers loaded into the kernel.

So you can compare the hash of programs that run automatically when the OS starts against the collection of hashes of "known" software provided by the NSRL (NIST National Software reference Library).

  • It lists executables that run, DLLs loaded Is it possible to list the DLL files loaded by a given runing software in Python or any other programming language ? Can you give me a hint/link, please ? – user45139 Jul 17 '14 at 14:06
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    Use a high or a middle level languages instead (like C++, C). For example the following sample code list the subkeys of a specific key : msdn.microsoft.com/en-us/library/windows/desktop/… – TMR_OS Jul 17 '14 at 14:11
  • I succeeded to do the same things in Python 2 weeks ago. But I do not think that listing the subkeys relfects the loaded DLLs by a running software. – user45139 Jul 17 '14 at 14:17
  • Or do you mean a subkey appears in the windows registry only if its DLL file is invoked/called ? – user45139 Jul 17 '14 at 14:24
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    Yes, but if you are trying to Monitor/Intercept application calls to DLL at runtime check this one : stackoverflow.com/questions/220515/… – TMR_OS Jul 17 '14 at 16:59

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