BKDR_FYNLOSKI.YYSYL
Backdoor:Win32/Fynloski (Microsoft); W32.Golroted (Symantec); HEUR:Trojan.Win32.Generic (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Atros5.CQZA (AVG)
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
TECHNICAL DETAILS
626,688 bytes
EXE
No
17 Jul 2017
Arrival Details
This Backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This Backdoor creates the following folders:
- %User Profile%\Application Data\dclogs
(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)
Other System Modifications
This Backdoor adds the following registry keys:
HKEY_CURRENT_USER\Software\DC3_FEXEC
It adds the following registry entries:
HKEY_CURRENT_USER\Software\DC3_FEXEC
6/26/2017 at 6:54:52 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
Dropping Routine
This Backdoor drops the following files:
- %User Profile%\Application Data\update.exe
- %User Temp%\z268
- %User Temp%\cryptme.execryptme.exe
(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
Other Details
This Backdoor connects to the following possibly malicious URL:
- {BLOCKED}1.61.145
This report is generated via an automated analysis system.
SOLUTION
9.8
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software
- DC3_FEXEC
Step 3
Delete this registry value
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\DC3_FEXEC
- 6/26/2017 at 6:54:52 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
Step 4
Search and delete these components
- %User Profile%\Application Data\update.exe
- %User Temp%\z268
- %User Temp%\cryptme.execryptme.exe
Step 5
Search and delete this folder
- %User Profile%\Application Data\dclogs
Step 6
Scan your computer with your Trend Micro product to delete files detected as BKDR_FYNLOSKI.YYSYL. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
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