Remote desktop software has become an essential tool for IT administrators, managed service providers, and businesses that provide technical support. While these platforms simplify remote access, they also require careful monitoring of account security, device associations, and licensing.

This case study describes a real-world investigation where an organization discovered an unknown AnyDesk Implicit Client associated with its Standard License. Despite multiple security measures—including password changes, license key reset, removal of team members, and enabling Two-Factor Authentication (2FA)—the unknown client continued to appear in the AnyDesk Management Portal and was observed initiating remote sessions.

To protect privacy, all Client IDs, names, aliases, and other identifying information have been changed.

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Background

An IT company using an AnyDesk Standard License noticed an unexpected remote connection popup on one of its support computers.

The popup disappeared almost immediately before any information about the connecting computer could be identified.

Initially, this appeared to be an ordinary unsolicited connection request.

However, further investigation revealed a much more interesting situation.

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Initial Symptoms

The administrator noticed:

• Brief incoming AnyDesk popup
• Connection automatically disconnected
• Unknown client listed under Implicit Clients
• Unknown client remained online continuously
• Unknown client appeared active for several hours
• Unknown client was visible in Portal Session Reports

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Privacy Information

For privacy reasons, the following values have been modified.

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Environment

• AnyDesk Standard License
• Windows 11
• Latest AnyDesk Client
• Two-Factor Authentication Enabled
• Team Management Enabled
• Single Licensed Computer

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Investigation Process

Step 1 – Verify Local Installation

The administrator first verified that only one installation of AnyDesk existed.

PowerShell confirmed:

• Single executable
• Single service
• Single configuration
• Single registered Client ID

No duplicate installations were found.

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Step 2 – Verify Client Identity

The configuration files confirmed that the local workstation was using its expected Client ID and alias.

No unexpected configuration changes were detected.

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Step 3 – Review Trace Logs

The AnyDesk trace logs revealed:

• Incoming session request from an unknown client
• Stable Client Fingerprint
• Connection negotiation
• Authentication challenge
• Connection termination

Interestingly, the logs never confirmed a successful unattended session.

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Initial Security Actions

The administrator immediately performed several security actions.

Password Changed

The AnyDesk account password was changed.

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License Key Reset

The Standard License Key was reset.

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Two-Factor Authentication

2FA was enabled and tested successfully.

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Team Members Removed

All additional Team Members were removed.

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Unattended Access Disabled

Permanent password authentication was disabled.

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Unexpected Discovery

Despite all security measures:

• Unknown client remained listed as an Implicit Client.
• Unknown client remained online.
• Unknown client continued appearing in Portal reports.
• Session history showed active remote sessions.

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Session Report Analysis

The exported CSV report showed:

• Multiple remote sessions initiated by the unknown client.
• Sessions lasting several minutes.
• Connections to multiple remote IDs.
• Normal closure of sessions.

The administrator also observed their own intentional diagnostic connection attempts during testing.

These entries were expected and clearly distinguishable from the unknown client's activity.

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Log Analysis

Review of trace logs showed:

• Authentication challenge issued.
• Connection establishment.
• Connection reuse.
• Connection closure.

No definitive evidence indicated that the unknown client successfully gained unattended control of the administrator's workstation.

Instead, the logs suggested communication between AnyDesk services rather than successful desktop control.

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Local System Verification

The administrator additionally verified:

• Windows Event Viewer
• Running Processes
• Installed Applications
• Startup Entries
• Configuration Files
• Background Services

No hidden AnyDesk installation or duplicate Client ID was found.

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Security Measures Performed

The following actions were completed:

✔ Password changed multiple times

✔ License Key reset

✔ Two-Factor Authentication enabled

✔ Team Members removed

✔ Unattended Access disabled

✔ Local AnyDesk installation verified

✔ Session logs exported

✔ Trace logs analyzed

✔ Fingerprints verified

✔ Portal reports reviewed

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Technical Observations

Several interesting observations were made.

Stable Fingerprint

The unknown client always presented the same fingerprint.

This strongly suggested it was one genuine AnyDesk installation rather than randomly generated IDs.

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Persistent Association

The unknown client survived:

• Password changes
• License reset
• 2FA activation

This suggested the association might not simply be caused by credential theft.

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Active Sessions

Portal reports showed that the unknown client was actively establishing remote sessions with other systems.

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Continuous Online Status

The client frequently remained online for many consecutive hours.

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Possible Technical Explanations

Several possibilities were considered.

Historical Device Association

A previously associated client remained linked to the account.

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Authentication Token Persistence

The client retained valid authentication tokens.

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License Backend Synchronization Issue

A backend licensing synchronization problem continued associating the client.

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Account Migration Artifact

Historical licensing information remained linked after account changes.

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What Was Ruled Out

The investigation ruled out:

• Malware on local workstation
• Duplicate AnyDesk installations
• Hidden services
• Multiple Client IDs
• Incorrect local configuration
• Windows Event Log evidence of compromise

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Escalation to Vendor

Because all local troubleshooting had been completed, the issue was escalated to AnyDesk Support with:

• Session Reports
• Trace Logs
• Screenshots
• Fingerprint Information
• License Details
• Security Timeline

The support request specifically asked the vendor to:

• Identify the authenticated account associated with the unknown client.
• Verify backend licensing associations.
• Revoke authentication tokens.
• Remove any incorrect client association.

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Lessons Learned

This investigation demonstrates several important security practices:

• Regularly monitor Implicit Clients.
• Review session history.
• Export logs before making changes.
• Enable Two-Factor Authentication.
• Disable Unattended Access when not required.
• Reset license keys if unauthorized devices appear.
• Escalate persistent licensing issues with supporting evidence.

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Best Practices

• Enable 2FA for every remote access account.
• Use strong unique passwords.
• Periodically review Implicit Clients.
• Review Portal Session Reports.
• Remove unused Team Members.
• Disable permanent unattended passwords unless required.
• Keep AnyDesk updated.
• Preserve logs before troubleshooting.
• Audit remote sessions regularly.

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Conclusion

This case study illustrates that not every suspicious client association indicates a successful system compromise. Thorough log analysis, configuration verification, and systematic troubleshooting can help distinguish between local security issues and potential backend licensing or account association problems.

When a client remains associated with an account despite password changes, license resets, and 2FA, it is appropriate to escalate the case to the software vendor with comprehensive technical evidence rather than relying solely on additional local troubleshooting.