Digital Forensics & Incident Response & Reverse Engineering
Have you ever encountered on-disk artifacts originating from another system?
Typically, this is something you see when a custom operating system image had been deployed to multiple computers by IT staff (on-disk artifacts appeared before the image is captured become a part of that image).
But there are some minor artifacts existing in installation images coming from Microsoft!
This is a reply to the Sunday Funday 4/5/20 challenge. The goal of this post is to document the process, not just the results. You have been warned.
The Background Activity Moderator (BAM) is a Windows 10 thing that does… something! Because we don’t know much about it.
We know that this thing provides evidence of execution by listing executables under the following registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\bam\State\UserSettings\<User SID>
Each piece of evidence is stored as a registry value (REG_BINARY), its name is set to an executable path and its data is set to a binary structure with a FILETIME timestamp inside (this is believed to be the last execution timestamp).
In the Linux world, a deleted file which is still open isn’t actually removed from a disk. Instead, it’s just unlinked from the directory structure. This is why a system call used to remove files is named “unlink”.
unlink() deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse.
If the name was the last link to a file but any processes still have the file open, the file will remain in existence until the last file descriptor referring to it is closed.
(Source.)
The same behavior can be observed in other Unix-like operating systems.
But in Windows 10, similar behavior can be seen too!
Many unexpected things happen under the hood when you do live forensics. Tools used to acquire data from running Windows systems often utilize direct access to logical drives to copy locked files and extract NTFS metadata. But did you know that NTFS metadata is updated when you read a logical drive directly?
Continue reading “You write to a logical drive when you read from it”
There are forensic tools capable of carving file records and index entries ($I30) from memory dumps, but there is much more NTFS-related metadata which isn’t exposed by usual memory forensics frameworks. For example, file control blocks.
Continue reading “Carving file control blocks from memory dumps”
Here is a list of open research topics in Windows forensics. All topics in this list are relevant to my research. Feel free to pick one for your research. Originally, I wrote this list for myself, but it’s better to make it public.
More topics and ideas (in other areas too) can be found here and here.
During the development of the parser for shadow copies, I observed many systems containing invalid data in shadow copies. For unknown reasons, some allocated files may contain null blocks instead of valid data blocks as well as blocks of data which should not be there.
Continue reading “Things you probably didn’t know about shadow copies”
Memory images, page files, hibernation files, crash dumps are standard targets for memory forensics. But there are unusual ones: for example, chunks of disclosed (leaked) uninitialized kernel memory found on a drive.
Continue reading “Forensic analysis of disclosed uninitialized kernel memory”
No operation on a file is allowed to include unallocated (deleted) data into the user-readable area of that file. Otherwise, an unprivileged program could read data from a deleted file even if such access was forbidden when this file was allocated.
But this is not an issue when dealing with files readable by privileged programs only (because such programs can read allocated and unallocated data from a file system directly). However, allocated files containing pieces of unallocated data are very rare (unlike the slack space, such data is a part of file’s data).
Continue reading “NTFS: unallocated data marked as allocated”
In the official NTFS implementation, all metadata changes to a file system are logged to ensure the consistent recovery of critical file system structures after a system crash. This is called write-ahead logging.
The logged metadata is stored in a file called “$LogFile”, which is found in a root directory of an NTFS file system.
Currently, there is no much documentation for this file available. Most sources are either too high-level (describing the logging and recovery processes in general) or just contain the layout of key structures without further description.
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