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What is DecUsername?

The Malwarebytes research team has determined that DecUsername is a crypto currency miner. These miners are designed to earn cryptocurrency by using system resources.

How do I know if my computer is affected by DecUsername?

You may see this Scheduled Task with the name Dec + %Username% :


and some users experienced a prompt related to krk.tmp asking "how do you want to open this file?"

[Update 11/6/2017] We now also see the filenames klk.tmp and revopartner.tmp besides krk.tmp

How did DecUsername get on my computer?

Miners use different methods for distributing themselves. This particular one was installed by a trojan.

How do I remove DecUsername?

Our program Malwarebytes can detect and remove this miner.

  • Please download Malwarebytes to your desktop.
  • Double-click mb3-setup-consumer-{version}.exe and follow the prompts to install the program.
  • Then click Finish.
  • Once the program has fully updated, select Scan Now on the Dashboard. Or select the Threat Scan from the Scan menu.
  • If another update of the definitions is available, it will be implemented before the rest of the scanning procedure.
  • When the scan is complete, make sure that all Threats are selected, and click Remove Selected.
  • Restart your computer when prompted to do so.
Is there anything else I need to do to get rid of DecUsername?
  • After the reboot you can remove the DecUsername entry from your list of installed Programs and Features if it belonged to the Trojan.
How would the full version of Malwarebytes help protect me?

We hope our application and this guide have helped you eradicate this trojan.

As you can see below the full version of Malwarebytes would have protected you against the DecUsername trojan. It would have warned you before the trojan could install itself, giving you a chance to stop it before it became too late.


Technical details for experts

Possible signs in FRST logs:
 () C:\Users\{username}\AppData\Local\Temp\krk.tmp
 HKCU\...\Run: [Win64svc] => krk.tmp [389632 2017-10-24] ()

Task: {347EA87B-0F3A-466E-B3F3-9B27062D1720} - System32\Tasks\Dec{username} => C:\Users\{username}\AppData\Local\Temp\krk.tmp [2017-10-24] () <==== ATTENTION
Malwarebytes log:

-Log Details-
Scan Date: 10/30/17
Scan Time: 9:20 AM
Log File: 4275d509-bd4b-11e7-b513-080027750297.json
Administrator: Yes

-Software Information-
Components Version: 1.0.212
Update Package Version: 1.0.3126
License: Premium

-System Information-
OS: Windows 7 Service Pack 1
CPU: x64
File System: NTFS
User: {computername}\{username}

-Scan Summary-
Scan Type: Threat Scan
Result: Completed
Objects Scanned: 331986
Threats Detected: 11
Threats Quarantined: 11
Time Elapsed: 3 min, 20 sec

-Scan Options-
Memory: Enabled
Startup: Enabled
Filesystem: Enabled
Archives: Enabled
Rootkits: Disabled
Heuristics: Enabled
PUP: Detect
PUM: Detect

-Scan Details-
Process: 0
(No malicious items detected)

Module: 0
(No malicious items detected)

Registry Key: 3
Trojan.Agent.TskLnk, HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree\Dec{username}, Delete-on-Reboot, [8813], [-1],0.0.0
Trojan.Agent.TskLnk, HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks\{347EA87B-0F3A-466E-B3F3-9B27062D1720}, Delete-on-Reboot, [8813], [-1],0.0.0
Trojan.Agent.TskLnk, HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Plain\{347EA87B-0F3A-466E-B3F3-9B27062D1720}, Delete-on-Reboot, [8813], [-1],0.0.0

Registry Value: 1
RiskWare.BitCoinMiner.TskLnk, HKCU\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\RUN|WIN64SVC, Delete-on-Reboot, [9165], [451415],1.0.3126

Registry Data: 0
(No malicious items detected)

Data Stream: 0
(No malicious items detected)

Folder: 0
(No malicious items detected)

File: 6
RiskWare.Agent.E, C:\USERS\{username}\APPDATA\LOCAL\TEMP\SOURSE.EXE, Delete-on-Reboot, [1050], [449494],1.0.3126
Trojan.Agent.TskLnk, C:\USERS\{username}\APPDATA\LOCAL\TEMP\KRK.TMP, Delete-on-Reboot, [8813], [451376],1.0.3126
Trojan.Agent.TskLnk, C:\WINDOWS\SYSTEM32\TASKS\Dec{username}, Delete-on-Reboot, [8813], [-1],0.0.0
Trojan.Injector.TskLnk, C:\USERS\{username}1\APPDATA\LOCAL\TEMP\KRK.TMP, Delete-on-Reboot, [9199], [451445],1.0.3126
RiskWare.BitCoinMiner.TskLnk, C:\USERS\{username}\DESKTOP\778899.EXE, Delete-on-Reboot, [9165], [451409],1.0.3126
Trojan.BitCoinMiner, C:\USERS\{username}\APPDATA\LOCAL\TEMP\MRM.TMP, Delete-on-Reboot, [78], [450839],1.0.3126

Physical Sector: 0
(No malicious items detected)

As mentioned before the full version of Malwarebytes could have protected your computer against this threat.
We use different ways of protecting your computer(s):
  • Dynamically Blocks Malware Sites & Servers
  • Malware Execution Prevention
Save yourself the hassle and get protected.


Edited by Metallica
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