1. A computer with a mouse, keyboard and monitor
2. The Steam client
3. Your game running on Source SDK Base 2006
4. Knowledge on how to extract a zip file archive and how to move files

the Steam release of NEOTOKYO and Fortress Forever are not affected as they have already been patched since 2017
The Ship and Dark Messiah Might and Magic Multiplayer are affected with no way to apply the patch shown in the guide

For Dark Messiah there is Phantasma which is a reimplementation of hl2master, instructions on how to patch Dark Messiah: Might and Magic multiplayer can be found here[github.com]

SDK 2007 games such as Age of Chivalry or D.I.P.R.I.P. Warm Up are not affected by this issue

This is not a definitive full list of all Multiplayer SDK 2006 games but its pretty overwhelming.

First close the Source game you are playing.
Secondly, download fix-server-browser.zip (3.28 MB)[www.mediafire.com]
The files in the zip file are obtained from NEOTOKYO° and have been packaged for this guide.

Then after you have downloaded fix-server-browser.zip, go to your Source SDK Base 2006 folder. If you don't know how to do this then this image will help you.

After a file browser opens on the Source SDK Base folder, you'll need to extract fix-server-browser.zip to the folder. If it prompts you to overwrite any files, hit yes

Now launch the game again and open the server browser, if you see something like the below screenshot then congratulations! you are ready to play
otherwise if you see just "There are no internet games listed on the master server that pass your filter settings." then this means it's working too, albeit there is no servers hosted for the game you are trying to play

This part of the guide assumes you already have a SDK 2006 dedicated server, if you are a regular player and do not plan to host any servers then skip this guide.

There's three DLL files that you will need to update, these are "steamclient.dll", "tier0_s.dll", "vstdlib_s.dll"

The said DLL files are outdated and will not announce to the master server. You can usually find updated copies in your Steam directory (where Steam.exe resides), if you manage to find these then copy to your SDK 2006 dedicated server, if you get any prompt to overwrite any files, hit yes.

After doing so edit your server configuration to include "sv_master_legacy_mode 0".

You should be able to launch the server and see "VAC secure mode is activated."

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If you are unable to find the mentioned DLL files then the guide E.Y.E. multiplayer server Linux setup and configuration by Nomotien explains how to do it in 3 methods.

Otherwise if you are just setting up a new SDK 2006 server then I suggest to just get NEOTOKYO Dedicated Server (appid 313600) as it already includes the mentioned fixes, just make sure to edit steam_appid.txt to be "215" (without quotes) instead of the appid for NEOTOKYO

If this guide has helped you, make sure to like and comment to say that it worked. Otherwise if you are still confused feel free to comment on this guide and I will make sure to reply back.

This guide will not work with Dark Messiah: Might and Magic Multiplayer and The Ship as they run on special versions of SDK 2006 and this fix will not work with them.

I also do not take credit for the patch itself as it is not mine.