Viotto Keylogger: Freemium Keylogger for the Skids

The PhishMe Research team recently received a campaign escalated by one or our analysts. We’ll explore the campaign delivery, malicious attachments, and analysis of the malicious attachments, and we’ll provide a simple method for extracting the credentials being used for this keylogger family’s data exfiltration.


The PhishMe Triage platform allows SOC analysts to identify, analyze, and respond to email threats that have targeted their organization. For this particular campaign, the suspicious email had an ARJ archive attachment, which contained a Windows PE32 executable.

lureAlthough Windows OS does not natively open archive files with the ARJ extension, a number of third-party applications, such as 7zip, will be able to extract these rarely-used archives. The content of the archive is a single PE32 executable name “DOCUMENT-71956256377.pdf.exe” which is a packed Viotto Keylogger sample, intentionally named with a double extension to entice victims to click and execute the malware.


Malicious attachment contains executable.

Since this malware was written in VB6, we can decompile the unpacked, malicious binaries to verify our classification. By viewing the VB6 forms, we can see that the hidden Form1 contains the name of Viotto Keylogger:


Decompiled VB6 forms.

Now that we have seen an example of how this malware propagates in the wild, let’s examine the family itself. When an analyst has access to a malware’s builder (an application that enables the easy customization of malware samples), we can save precious reverse engineering time by analyzing its capabilities and features to better understand how this malware behaves.


Most of the indicators that comprise a Viotto Keylogger infection can be set at build time when the actor creates the stub (the malware sample that infects a victim’s computer). In the public version 3.0.2 of the builder, the malicious actor can specify where the keylogger’s logs will be stored, the installation method for persistence, and the delivery method of the logs via SMTP and/or FTP. In the paid, private version of the builder, the actor is able to control even more settings, such as encrypting the Keylogger logs with RC4 with a hardcoded key and enabling a Screen Capture feature that periodically sends screenshots of the victim’s desktop back to the actor. Another feature included in both versions that is not highlighted in the builder’s options is the ability to capture all text copied to the victim’s clipboard.


VKL Builder’s main screen.

The storage location option for the keylogger log files can be set by the malicious actor at build time. They also have the ability to specify a custom log filename and to set hidden file attributes. The log files can be saved in the following locations on the infected machine’s disk:

  • Root (C:\)
  • Windows (C:\Windows)
  • System32 (C:\Windows\System32)
  • Program Files (C:\Program Files)
  • Application Path (copied where originally executed)
  • Temp (C:\Users\{username}\AppData\Local\Temp)
  • AppData (C:\Users\{username}\AppData\Roaming)

Options where keylogger logs will be stored.


As described above, depending on the settings enabled during built time of the stub, the actor has the ability to enable infection persistence through reboots of the infected machine. The actor can also select the option to save a copy of the executable which has the same file system options as the log file storage locations. The copy of this executable can then be executed during Windows’ start up events for persistence through computer restarts. Although multiple instances of the stub can be launched by selecting any combination of startup entries, the stub ensures it’s the only process currently running by checking the mutex (a program object lock used to avoid multiple instances of the same malware from running). The default mutex is “ViottoLogger”; however, this setting can also be changed in the builder. The following startup registry keys are viable options:

  • Current User\Run (HKCU\Software\Microsoft\Windows\CurrentVersion\Run)
  • Local Machine\Run (HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run)
  • Winlogon\Shell (HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell)
  • Winlogon\Userinit (HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Userinit)
  • Explorer\Run (HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run)

Windows startup persistence options.

Keylogger Data Exfil

Viotto Keylogger is capable of sending the recorded keystrokes, clipboard contents, and screenshots to the perpetrator in an email (via SMTP) or to a file server (via FTP). The email option can be delivered to open relays that do not require authentication or to accounts that require authentication over SMTP using Transport Layer Security (TLS). By utilizing TLS, the account credentials and email contents will be encrypted in transit. Most of the VB6 code in this keylogger was copied from sources freely available on the internet, as indicated in the builder’s About screen:


Extracting Exfil Credentials

Skids wishing to use this malware creator be forewarned: your email and FTP credentials can be easily obtained! Although most of these samples in the wild will be packed, a quick and easy way to extract the malware actor’s credentials being used for victim data exfiltration is by analyzing the application’s process memory. Analysts are not only able to extract this information on the same machine utilizing a program such as Process Hacker, but personally, I prefer keeping my memory analysis tools outside of the infected machine by analyzing full VM RAM dumps with either the Rekall or Volatility memory analysis frameworks. We can also extract the malware sample’s configuration, including any SMTP/ FTP exfil credentials, statically. The malware sample’s configuration is stored plaintext in the Resources section of the stub:


The decompiled FindResource section loads the stub configuration.

The PhishMe Research team also wrote a Python script to extract the Viotto Keylogger configuration from an unpacked sample:



The recent sighting of the freely-available Viotto Keylogger in the wild reminds us that cybercrime has a low barrier to entry and that tools built years ago continue to be used to exploit unsuspecting users. PhishMe Simulator trains and encourages users to recognize and report the type of email messages that are delivering this threat. The next step is to act on those reports, and PhishMe Triage enables your team to sift through all reports and quickly and efficiently act on the ones that pose a threat to your organization. Click here to learn more.


Related SHA256 Hashes




Download the Viotto Keylogger yara rule or the configuration extractor.


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