mirror of
https://github.com/carlospolop/hacktricks
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152 lines
8 KiB
Markdown
152 lines
8 KiB
Markdown
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# Anti-Forensic Techniques
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## Timestamps
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An attacker may be interested in **changing the timestamps of files** to avoid being detected.
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It's possible to find the timestamps inside the MFT in attributes `$STANDARD_INFORMATION` __and __`$FILE_NAME`.
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Both attributes have 4 timestamps: **Modification**, **access**, **creation**, and **MFT registry modification** \(MACE or MACB\).
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**Windows explorer** and other tools show the information from `$`**`STANDARD_INFORMATION`**.
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### TimeStomp - Anti-forensic Tool
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This tool **modifies** the timestamp information inside **`$STANDARD_INFORMATION`** **but** **not** the information inside **`$FILE_NAME`**. Therefore, it's possible to **identify** **suspicious** **activity**.
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### Usnjrnl
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The **USN Journal** \(Update Sequence Number Journal\), or Change Journal, is a feature of the Windows NT file system \(NTFS\) which **maintains a record of changes made to the volume**.
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It's possible to use the tool [**UsnJrnl2Csv**](https://github.com/jschicht/UsnJrnl2Csv) to search for modifications of this record.
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The previous image is the **output** shown by the **tool** where it can be observed that some **changes were performed** to the file.
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### $LogFile
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All metadata changes to a file system are logged to ensure the consistent recovery of critical file system structures after a system crash. This is called [write-ahead logging](https://en.wikipedia.org/wiki/Write-ahead_logging).
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The logged metadata is stored in a file called “**$LogFile**”, which is found in a root directory of an NTFS file system.
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It's possible to use tools like [LogFileParser](https://github.com/jschicht/LogFileParser) to parse this file and find changes.
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Again, in the output of the tool it's possible to see that **some changes were performed**.
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Using the same tool it's possible to identify to **which time the timestamps were modified**:
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* CTIME: File's creation time
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* ATIME: File's modification time
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* MTIME: File's MFT registry modifiction
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* RTIME: File's access time
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### `$STANDARD_INFORMATION` and `$FILE_NAME` comparison
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Another way to identify suspicions modified files would be to compare the time on both attributes looking for **mismatches**.
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### Nanoseconds
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**NTFS** timestamps have a **precision** of **100 nanoseconds**. Then, finding files with timestamps like 2010-10-10 10:10:**00.000:0000 is very suspicious**.
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### SetMace - Anti-forensic Tool
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This tool can modify both attributes `$STARNDAR_INFORMATION` and `$FILE_NAME` . However, from Windows Vista it's necessary a live OS to modify this information.
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## Data Hiding
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NFTS uses a cluster and the minimum information size. That means that if a file occupies uses and cluster and a half, the **reminding half is never going to be used** until the files is deleted. Then, it's possible to **hide data in this slack space**.
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There are tools like slacker that allows to hide data in this "hidden" space. However, an analysis of the `$logfile` and `$usnjrnl` can show that some data was added:
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Then, it's possible to retrieve the slack space using tools like FTK Imager. Note that this can of tools can save the content obfuscated or even encrypted.
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## UsbKill
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This is a tool that will **turn off the computer is any change in the USB** ports is detected.
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A way to discover this would be to inspect the running processes and **review each python script running**.
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## Live Linux Distributions
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These distros are **executed inside the RAM** memory. The only way to detect them is **in case the NTFS file-system is mounted with write permissions**. If it's mounted just with read permissions it won't be possible to detect the intrusion.
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## Windows Configuration
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It's possible to disable several windows logging methods to make the forensics investigation much harder.
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### Disable Timestamps - UserAssist
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This is a registry key that maintains dates and hours when each executable was run by the user.
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Disabling UserAssist requires two steps:
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1. Set two registry keys, `HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Start_TrackProgs` and `HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Start_TrackEnabled`, both to zero in order to signal that we want UserAssist disabled.
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2. Clear your registry subtrees that look like `HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\UserAssist\<hash>`.
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### Disable Timestamps - Prefetch
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This will save information about the applications executed with the goal of improving the performance of the Windows system. However, this can also be useful for forensics practices.
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* Rexecute `regedit`
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* Select the file path `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SessionManager\Memory Management\PrefetchParameters`
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* Right-click on both `EnablePrefetcher` and `EnableSuperfetch`
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* Select Modify on each of these to change the value from 1 \(or 3\) to 0
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* Restart
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### Disable Timestamps - Last Access Time
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Whenever a folder is opened from an NTFS volume on a Windows NT server, the system takes the time to **update a timestamp field on each listed folder**, called the last access time. On a heavily used NTFS volume, this can affect performance.
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1. Open the Registry Editor \(Regedit.exe\).
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2. Browse to `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem`.
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3. Look for `NtfsDisableLastAccessUpdate`. If it doesn’t exist, add this DWORD and set its value to 1, which will disable the process.
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4. Close the Registry Editor, and reboot the server.
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### Delete USB History
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All the **USB Device Entries** are stored in Windows Registry Under **USBSTOR** registry key that contains sub keys which are created whenever you plug a USB Device in your PC or Laptop. You can find this key here H`KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\USBSTOR`. **Deleting this** you will delete the USB history.
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You may also use the tool [**USBDeview**](https://www.nirsoft.net/utils/usb_devices_view.html) to be sure you have deleted them \(and to delete them\).
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Another file that saves information about the USBs is the file `setupapi.dev.log` inside `C:\Windows\INF`. This should also be deleted.
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### Disable Shadow Copies
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**List** shadow copies with `vssadmin list shadowstorage`
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**Delete** them running `vssadmin delete shadow`
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You can also delete them via GUI following the steps proposed in [https://www.ubackup.com/windows-10/how-to-delete-shadow-copies-windows-10-5740.html](https://www.ubackup.com/windows-10/how-to-delete-shadow-copies-windows-10-5740.html)
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To disable shadow copies:
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1. Go to the Windows start button and type "services" into the text search box; open the Services program.
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2. Locate "Volume Shadow Copy" from the list, highlight it, and then and the right-click > Properties.
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3. From the "Startup type" drop-down menu, select Disabled, and then click Apply and OK.
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It's also possible to modify the configuration of which files are going to be copied in the shadow copy in the registry `HKLM\SYSTEM\CurrentControlSet\Control\BackupRestore\FilesNotToSnapshot`
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### Overwrite deleted files
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* You can use a **Windows tool**: `cipher /w:C` This will indicate cipher to remove any data from the available unused disk space inside the C drive.
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* You can also use tools like [**Eraser**](https://eraser.heidi.ie/)
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### Delete Windows event logs
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* Windows + R --> eventvwr.msc --> Expand "Windows Logs" --> Right click each category and select "Clear Log"
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* `for /F "tokens=*" %1 in ('wevtutil.exe el') DO wevtutil.exe cl "%1"`
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* `Get-EventLog -LogName * | ForEach { Clear-EventLog $_.Log }`
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### Disable Windows event logs
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* `reg add 'HKLM\SYSTEM\CurrentControlSet\Services\eventlog' /v Start /t REG_DWORD /d 4 /f`
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* Inside the services section disable the service "Windows Event Log"
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* `WEvtUtil.exec clear-log` or `WEvtUtil.exe cl`
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### Disable $UsnJrnl
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* `fsutil usn deletejournal /d c:`
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