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RealVNC error: Too many security failures – Resolved

Before diving into the solution for “RealVNC error too many security failures”, let’s look at what causes this message.

According to our experts, VNC Server comes with a ‘blacklisting’ scheme. This involves blocking an IP address after five failed connection attempts. This security feature is responsible for preventing DOS and Brute Force attacks.

Furthermore, the IP address is blocked initially for ten seconds. This is doubled for each failed attempt after the initial unsuccessful attempt.

Fortunately, a successful connection from the IP address will reset the blacklist timeout as well. This specific feature is built into the VNC server. It does not rely on OS support.

According to our experts, we can manually reset the timeout by not attempting a connection for a while. Alternatively, we can restart the VNC server software or the system running the VNC server with these steps:

• First, connect remotely to the VNC server.
• Then, if the server is configured to start automatically when Linux boots up then enter “service vncserver restart” into the terminal.

  If the server is not set up to automatically start up, enter the normal kill and restart commands.

In case you are still running into trouble, our experts suggest ensuring the correct username and password have been entered.

Alternatively, we can run the following command on the VNC server machine. We can replace 5 with another number:

vncconfig -display :5 -set BlacklistTimeout=0 -set BlacklistThreshold=1000000

Our experts would like to point out that if we are using ThightVNC java client, we can connect only by modifying the VNC client’s port to 5002, 5003, etc.

Let us know in the comments which of the above methods helped you overcome RealVNC error: Too many security failures.

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Conclusion

To conclude, our Support Engineers gave us a closer look at RealVNC error: Too many security failures. We learned about the root cause behind this error and how to resolve it.