FS_FindEvil

The findevil forensic directory

IMPORTANT NOTE! - FindEvil is work in progress. FindEvil will miss certain types of malware while quickly locating others. FindEvil only detects user-mode malware. FindEvil have false positives in its current implementation. FindEvil is primarily available on 64-bit Windows 10 and 11

The directory findevil exists as a sub-directory to the forensic directory at /forensic/findevil. To active findevil and scan for indicators of evil forensic mode must be activated.

FindEvil locates signs of malware by analyzing select indicators of evil. FindEvil swiftly discovers certain code injection techniques commonly employed by malware while it is completely unaware of other not-yet implemented indicators.

FindEvil makes use of built-in Yara rules from Elastic for select functionality. To enable the rules the Elastic License 2.0 must be accepted first with start-up option: -license-accept-elastic-license-2-0.

The files in the findevil directories are listed in the table below:

File	Description
findevil.txt	Result file with possible detections of evil.
readme.txt	README file.
yara.txt	Detailed information about YR_* detections. ´
yara_rules.txt	YARA rules that triggered triggered detections.

Files in the findevil directory is read-only.

Description of findevil.txt

#       PID Process         Type        VirtualAddress   ModuleName
=======================================================================
0000   2188 spoolsv.exe     PE_INJECT   0000000001840000 ext_server_priv.x64.dll
0001    356 SecurityHealth  PE_NOLINK   00007ffd700d0000 AppCore.dll
0002    356 SecurityHealth  PE_NOLINK   00007ffd702d0000 Windows.Storage.dll
0003    356 SecurityHealth  PE_NOLINK   00007ffd71ad0000 Wldp.dll

...

#       PID Process         Type        VirtualAddress    PhysicalAddr              PTE Flags      VADVirtAddr  VadPhysAddr           VadPTE VadFlagsType   VadName
=============================================================================================================================================================================
04ef   1192 svchost.exe     PE_PATCHED  00007ffd723f2000  000000123000 0000000000123157 A rwx ffffbe8e75a83930 000070dee000 0a00000070dee121 A Image ---wxc \Windows\System32\msvcp_win.dll
04f0   1192 svchost.exe     PE_PATCHED  00007ffd723fe000  000054686000 0000000054686477 A rwx ffffbe8e75a83930 000003ce1000 0a00000003ce1121 A Image ---wxc \Windows\System32\msvcp_win.dll
04f1   5392 MicrosoftEdgeC  PE_PATCHED  00007ffd6f69d000  0000510af000 02000000510af005 A r-x ffffbe8e7a2341c0 00006f097000 8a0000006f097121 A Image ---wxc ndows\System32\CoreMessaging.dll
04f2   5392 MicrosoftEdgeC  PE_PATCHED  00007ffd6f6a0000  00005119c000 020000005119c005 A r-x ffffbe8e7a2341c0 00006f098000 8a0000006f098121 A Image ---wxc ndows\System32\CoreMessaging.dll                   
04fa   2188 spoolsv.exe     PRIVATE_RWX 0000000001840000  0000131a8000 08000000131a8867 A rwx ffffbe8e77e690b0 000000000000 0000000000000000 -       p-rwx-
04fb   2188 spoolsv.exe     PRIVATE_RWX 0000000001841000  000031629000 0800000031629867 A rwx ffffbe8e77e690b0 000000000000 0000000000000000 -       p-rwx-
04fc   2188 spoolsv.exe     PRIVATE_RWX 0000000001842000  00005f9aa000 080000005f9aa867 A rwx ffffbe8e77e690b0 000000000000 0000000000000000 -       p-rwx-
04fd   2188 spoolsv.exe     PRIVATE_RWX 0000000001843000  00001ffab000 080000001ffab867 A rwx ffffbe8e77e690b0 000000000000 0000000000000000 -       p-rwx-
0508   4312 svchost.exe     PRIVATE_RX  00000139cfe07000  000000000000 0000000000000015 A r-x ffffbe8e79f0a4c0 000000000000 0000000000000000 -       p-rw--
0509   1172 svchost.exe     NOIMAGE_RX  00007ff502202000  000000f00000 0000000000f00745 A r-x ffffbe8e7a1028a0 000000000000 0000000000000000 -       ------

Example

The example below shows the global forensic/findevil/findevil.txt and with indications of a cobalt strike infection in the svchost, powershell and rundll32 processes. Please note that it may take a few seconds to render the findevil.txt listing asynchronously from first folder access.

Indicators of Evil

Indicators of Evil are generally sorted by likelyhood and severeness. Some indicators are only reported a certain number of times before being suppressed.

YR_*	Yara based detections
Description:	YR_* are potential evils flagged by Yara scanning. See additional information for each scanning type.
False Positives:	MEDIUM: Yara rules are usually high-quality, but false positives exists.
Other:	Yara rules are mostly based on Elastic Security rules. Rules are disabled unless license is accepted. To enable, the Elastic License 2.0 License agreement must be accepted with command line option: -license-accept-elastic-license-2-0

Additional Information:

Type	Description
YR_TROJAN
YR_VULNDRIVER	Known vulnerable driver. Often used for evil, but not malicious in itself.
YR_HACKTOOL	Often used for offensive purposes, may be used in security audits as well.
YR_EXPLOIT
YR_SHELLCODE
YR_ROOTKIT
YR_RANSOMWARE
YR_WIPER
YR_BACKDOOR	Often legit remote management software, but often used for evil.
YR_GENERIC	Other classes of Yara rules.

---

AV_DETECT	Anti-Virus Detection
Description:	AV_DETECT reports malware detected by the anti-virus residing on the analyzed system.
False Positives:	LOW

---

PE_INJECT	Injected Modules
Description:	PE_INJECT locates malware by scanning for valid .DLLs and .EXEs with executable pages in their page tables located in a private (non-image) virtual address descriptor.
False Positives:	LOW
Side Effects:	Injected modules are loaded into the general module map and may be accessed as files and modules.

---

PEB_MASQ	PEB Masquerading
Description:	PEB_MASQ will flag PEB Masquerading attempts. If PEB_MASQ is detected please investigate further in /sys/proc/proc-v.txt
False Positives:	LOW
Side Effects:	PE_NOLINK findings are suppressed.

---

PE_HDR_SPOOF	Module PE header may be spoofed.
Description:	PE_HDR_SPOOF - Module PE header employs a known spoof technique.
False Positives:	LOW: May trigger on valid PE headers using one of the detected spoof techniques for legit reasons.

Additional Information:

Detects Low Alignment PE files - i.e. PE files in which everything is mapped into a single section overriding any section headers.

---

PEB_BAD_LDR	No Modules enumerated from PEB/LDR_DATA
Description:	BAD_PEB_LDR will flag if no in-process modules are enumerated from the PEB/LDR_DATA structures.
False Positives:	HIGH : Often trigger on corrupt PEB/LDR_DATA memory for non-malware reasons - such as paged out or otherwise unavailable memory; or drift during memory acquisition.
Side Effects:	PE_NOLINK findings are suppressed.

---

PROC_BAD_DTB	Invalid process DirectoryTableBase (DTB)
Description:	PROC_BAD_DTB will flag active processes with an invalid DirectoryTableBase (DTB) in the kernel _EPROCESS object.
False Positives:	HIGH: May trigger on corrupt memory as well as malware activities.

Additional Information:

In the case of a maliciously modified DirectoryTableBase/DTB/CR3 it may be possible to recover it manually.

This is done by looking at potential DTBs without any related process in the file dtb.txt in the /misc/procinfo/ module. If such entries are found they can be tested by writing them to the dtb.txt in the process root folder. This is likely to be some trial and error involved and is not something MemProcFS will do automatically.

---

PROC_NOLINK	Module not found in EPROCESS linked list
Description:	PROC_NOLINK will flag if the process does not exist in the kernel _EPROCESS linked list.
False Positives:	MEDIUM: May trigger on slightly corrupt memory as well as malware activities.

---

PROC_PARENT	Well known process has bad parent process
Description:	PROC_PARENT will flag if a well known process has a bad parent process.
False Positives:	MEDIUM: May trigger if another process has the same name as a well known process.

---

PROC_USER	Process is executing as non standard user
Description:	PROC_USER may trigger if well known processes are executing as a strange user. Example cmd.exe as SYSTEM.
False Positives:	MEDIUM: May trigger if another process has the same name as a well known process.

---

PROC_DEBUG	Processes with the SeDebugPrivilege
Description:	PROC_DEBUG flag non-SYSTEM processes with the SeDebugPrivilege.
False Positives:	MEDIUM: Also triggers on legit applications with the SeDebugPrivilege.

---

THREAD	Thread based detections.
Description:	THREAD flag various thread related issues. Detections are listed below. NO_IMAGE: Thread not started in image memory. PRIVATE_MEMORY: Thread started in private memory. BAD_MODULE: Thread started in module without legit entry point. LOAD_LIBRARY: Thread starting point is kernel32.dll!LoadLibrary. SYSTEM_IMPERSONATION: Thread impersonates SYSTEM. NO_RTLUSERTHREADSTART: Thread startup is not RtlUserThreadStart.
False Positives:	HIGH: Often flag legit SYSTEM_IMPERSONATION. Thread start at LOAD_LIBRARY is sometimes used by legit products.

---

TIME_CHANGE	System Time Change
Description:	TIME_CHANGE reports a system time change backwards in time to a time before the boot time. A system time change is not malicious in itself but may provide important context.
False Positives:	LOW

---

PE_NOLINK	Unlinked Modules
Description:	PE_NOLINK locates malware in image virtual address descriptors which is not linked from the in-process PEB/Ldr lists.
False Positives:	HIGH : Often trigger on corrupt memory for non-malware reasons - such as paged out or otherwise unavailable memory; or drift during memory acquisition.

---

PE_PATCHED	Patched Modules
Description:	PE_PATCHED locates malware in image virtual address descriptors which executable pages (in the page tables) differs from kernel prototype memory.
False Positives:	HIGH : Commonly triggers on relocations predominantly in 32-bit processes. Number of pages reported is limited to 4 per VAD.

---

DRIVER_PATH	Kernel driver loaded from non-standard path
Description:	DRIVER_PATH flag kernel drivers that are loaded from a non-standard path. DRIVER_PATH also flag if no corresponding module could be located.
False Positives:	MEDIUM : Legit drivers aren't usually loaded from non-standard paths - but they exist. Missing modules may flag on corrupt memory.

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PRIVATE_RWX	Private Read/Write/Execute
Description:	PRIVATE_RWX locates malware with read/write/execute (RWX) pages in the page table which belongs to a private memory virtual address descriptor.
False Positives:	MEDIUM : RWX memory should be relatively rare on most systems; but in some processes with Just-In-Time code (JIT) it may be common. Number of pages reported is limited to 4 per VAD. Detection is avoided on some processes.

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NOIMAGE_RWX	No-Image Read/Write/Execute
Description:	NOIMAGE_RWX locates malware with read/write/execute (RWX) pages in the page table which does not belong to image (module) virtual address descriptors.
False Positives:	MEDIUM : RWX memory should be relatively rare on most systems; but in some processes with Just-In-Time code (JIT) it may be common. Number of pages reported is limited to 4 per VAD. Detection is avoided on some processes.

---

PRIVATE_RX	Private Read/Execute
Description:	PRIVATE_RX locates malware with read/execute (RX) pages in the page table which belongs to a private memory virtual address descriptor.
False Positives:	MEDIUM : RX memory should be relatively rare on most systems; but in some processes with Just-In-Time code (JIT) it may be common. Number of pages reported is limited to 4 per VAD. Detection is avoided on some processes.

---

NOIMAGE_RX	No-Image Read/Execute
Description:	NOIMAGE_RX locates malware with read/execute (RX) pages in the page table which does not belong to image (module) virtual address descriptors.
False Positives:	MEDIUM : RX memory should be relatively rare on most systems; but in some processes with Just-In-Time code (JIT) it may be common. Number of pages reported is limited to 4 per VAD. Detection is avoided on some processes.

---

UM_APC	User-Mode APC hook
Description:	UM_APC locates an APC hook - commonly used by malware to hide execution.
False Positives:	LOW

Additional Information:

In the Description field of the UM_APC detection the following data will be shown in order:

1. ApcNormalRoutine
2. ApcNormalContext Address and description
3. ApcSystemArgument1 Address and description
4. ApcSystemArgument2 Address and description
5. Thread ID (TID)

For Developers

The findevil sub-directories are implemented as a built-in native C-code plugin. The plugin source is located in the file modules/m_fc_findevil.c in the vmm project. Scanning for issues are implemented in plugins m_evil*.