5. Scan

First of all, THOR runs fine with the default settings. The recommended scan options are already active in the default scan.

5.1. Quick Start

Follow these steps to complete your first THOR scan

Make sure you've read the Before You Begin guide
Open a command line (cmd.exe) as Administrator
Navigate to the folder in which you've extracted the THOR package and placed the license file(s)
Start THOR with thor64.exe (macOS: thor-macos, Linux: thor-linux-64)
Wait until the scan has completed (this can take between 20 and 180 minutes)
When the scan is complete, check the text log and HTML report in the THOR program directory

5.2. Often Used Parameters

Parameter	Description
--soft	Reduce CPU usage, skip all checks that can consume a lot of memory (even if only for a few seconds)
--quick	Perform a Scan Modes (skips Eventlog and checks only the most relevant folders)
-e target-folder	Write all output files to the given folder

5.3. Parameters Possibly Relevant for Your User Case

Parameter

Description

-c, --cpulimit percentage

Reduce the average CPU load to the given percentage value. This can be helpful to reduce the load e.g. on server systems with real-time services or reduce the noise produced by fans on user laptops.

The specified value is a percentage value for the complete CPU. For example, --cpulimit 50 on a quad-core system limits THOR to using at most 50% of the available CPU time, which would be 2 cores.

--allhds

By default THOR scans only the C: partition on Windows machines and other files/folders only in cases in which some reference points to a different partition (e.g. configured web root of IIS is on D:\inetpub, registered service runs from D:\vendor\service)

--lookback days --globallookback

Only check the elements changed or created during the last X days in all available modules (reduces the scan duration significantly)

5.4. Risky Flags

This list contains flags that should better be avoided unless you know exactly what you're doing.

Parameter	Description
--intense	long runtime, stability issues due to disabled resource control
--c2-in-memory	many false positives on user workstations (especially browser memory)
--alldrives	long runtime, stability issues due to scan on network drives or other remote file systems
--mft	stability issues due to high memory usage
--dump-procs	stability issues, possibly high disk space usage (free disk space checks are implemented but may fail)
--full-registry	longer runtime, low positive impact

5.5. Lesser Known But Useful Flags

This list contains flags that are often used by analysts to tweak the scan in useful ways.

Parameter	Description
--allreasons	Show all reasons that led to a certain score
--printshim	Print all available SHIM cache entries into the log
--utc	Print all timestamps in UTC (helpful when creating timelines)
--string-context num-chars	Number of characters preceeding and following the string match to show in the output

5.6. Help and Debugging

You can use the following parameters to

Parameter	Description
--debug	Get debug information if errors occur
--help	Get a help with the most important scan options
--fullhelp	Get a help with all scan options

5.7. Examples

5.7.2. Logging to Syslog Server

The following command instructs THOR to log to a remote syslog server only.

C:\nextron\thor>thor64.exe --nohtml --nocsv --nolog -s syslog.server.net

5.7.3. Scan Run on a Single Directory

C:\nextron\thor>thor64.exe --lab -p C:\ProgramData
C:\nextron\thor>thor64.exe --lab -p I:\mounted\_image\disk1

IMPORTANT: This feature requires a forensic lab license type which is meant to be used in forensic labs.

You can imitate a lab scan without a lab license with these command line flags:

C:\nextron\thor>thor64.exe -a Filescan --intense --norescontrol --nosoft --cross-platform -p C:\ProgramData

5.7.4. Deactivate all file output - Syslog only

C:\nextron\thor>thor64.exe -s 10.1.5.14 --nohtml --nolog --nocsv

5.7.5. Save the result files to a different directory

C:\nextron\thor>thor64.exe -s 10.1.5.14 -e Z:\

5.7.6. Only scan the last 7 days of the Windows Eventlog and log files on disk

C:\nextron\thor>thor64.exe --lookback 7

5.7.7. Scan System with Defaults and Make a Surface Scan

By default, the surface scan (DeepDive) applies all YARA rules in "./custom-signatures" folder. In this example all output files are written to a network share.

C:\nextron\thor>thor64.exe --deepdivecustom -e \\server\share\thor_output\

5.7.8. Intense Scan and DeepDive on a Mounted Image

5.7.8.1. Mounted as Drive Z

C:\nextron\thor>thor64.exe --lab --deepdive -p Z:\

5.7.8.2. Mounted as /mnt

C:\nextron\thor>thor64.exe --lab --deepdive -p /mnt

IMPORTANT: Lab scanning mode requires a forensic lab license type which is meant to be used in forensic labs.

5.7.9. Scanning a Folder or Drive without a Forensic Lab License

You can achieve a similar (but not an equal) scan using a standard license and the following command line:

C:\nextron\thor>thor64.exe -a Filescan --intense --norescontrol --cross-platform --alldrives -p E:\

You can find more information on the advantages of a THOR Forensic Lab license here.

5.7.10. Throttled THOR Run (static throttling value)

Will restrict THOR's CPU usage in the long running modules “FileScan”, “Eventlog”, “LogScan” and “Registry” to 60%. Note that THOR automatically applies certain restrictions in automatic soft mode.

C:\nextron\thor>thor64.exe -c 60

5.7.11. Scan Multiple Paths

C:\nextron\thor>thor64.exe --lab -p C:\\ D:\\webapps E:\\inetpub

(non-existent directories will be automatically skipped)

5.7.12. Scan All Hard Drives (Windows Only)

C:\nextron\thor>thor64.exe --allhds

5.7.13. Don't Scan Recursively

To instruct THOR to scan a folder non-recursively use the :NOWALK suffix.

C:\nextron\thor>thor64.exe -a FileScan -p C:\Windows\System32:NOWALK

5.8. Run a Scan with Specific Modules

With the parameter -a you can run a single module or select a set of modules that you'd like to run.

Valid modules are:

Autoruns	DeepDive	Dropzone	EnvCheck
Filescan	Firewall	Hosts	LoggedIn
OpenFiles	ProcessCheck	UserDir	ServiceCheck
Users	AtJobs	DNSCache	Eventlog
HotfixCheck	LSASessions	MFT	Mutex
NetworkSessions	NetworkShares	RegistryChecks	Rootkit
SHIMCache	ScheduledTasks	WMIStartup

Run a Rootkit check only:

C:\nextron\thor>thor64.exe -a Rootkit

Run the Eventlog and file system scan:

C:\nextron\thor>thor64.exe –a Eventlog -a Filescan

5.9. PE-Sieve Integration

THOR integrates PE-Sieve, an open-source tool by @hasherezade to check for malware masquerading as benevolent processes.

PE-Sieve can be activated by using the --processintegrity flag. It runs on Windows as part of the ProcessCheck module and is capable of detecting advanced techniques such as Process Doppelganging.

When investigating infections, you can also raise the sensitivity of the integrated PE-Sieve beyond the default with --full-proc-integrity (at the cost of possible false positives).

THOR reports PE-Sieve results as follows:

Findings	THOR's Reporting Level
Replaced PE File	Warning
Implanted PE File	Warning
Unreachable File	Notice
Patched	Notice
IAT Hooked	Notice
Others	No Output in THOR

See the PE-Sieve documentation for more details on these values.

5.10. Multi-Threading

THOR 10.6 supports scanning a system with multiple threads in parallel, allowing for a significant increase in speed in exchange for a higher CPU usage.

To use this feature, use the --threads flag which allows you to specify THOR's number of parallel threads.

When using the --lab (Lab Scanning), --dropzone (sample drop zone) or --thunderstorm (Thunderstorm) command line flags, THOR will default to using as many threads as the system has CPU cores; otherwise, THOR will still default to running with a single thread.

Note: This mode is only available with the "Lab", "Thunderstorm" and "Incident Response" license type.

5.10.1. Enabled Modules

Not all modules support multi-threading. It is currently enabled in: File, Registry, Eventlog scanning and Thunderstorm and Dropzone service mode.