koumodgp

A server integrity and mod-compatibility plugin for dedicated Valheim servers.

koumodgp helps server admins keep their community consistent and fair. It verifies that every connecting player is running the mod set the server expects, and helps admins spot tampering. It is designed for legitimate server administration — it is installed and configured by the server owner, and every check it performs is in service of protecting that server's players.

The same koumodgp.dll is installed on the server and on clients; it detects its role at runtime (like AzuAntiCheat and other ServerSync-style plugins), so there is only one file to distribute.

What it does

• Mod whitelist — clients report their loaded BepInEx plugins; the server compares them to an admin-defined allow list and disconnects mismatches. Supports required and optional mods.
• Integrity check — detects code from unauthorized third-party injectors that patch the game at runtime (a common way cheats are added to a modded client).
• State audit — checks a small set of well-known game flags (god mode, fly, ghost, free build) that external trainers toggle. These are never set for a normal player.
• Program check (Windows clients) — matches running program names / window titles against an admin-provided list of known cheat tools.

Transparency about the program check

The program check (an optional, admin-configured feature) reads the names of running processes and top-level window titles so it can match them against the server's list of known cheat tools. This is the same approach used by other server anticheat plugins. Important points:

• It runs only when the server admin has added entries to the signature list. An empty list means it does nothing.
• The client uploads only match results ("a listed name matched") — never a list of your running programs. Your process list never leaves your machine.
• Servers should tell their players (via rules / MOTD) that an integrity check is in use.

Install

1. Put koumodgp.dll in BepInEx/plugins/ on the server and on each client.
2. Start the server once. It creates BepInEx/config/koumodgp.cfg and, under BepInEx/config/koumodgp/, allowed_mods.txt and signatures.txt (both start empty with examples).
3. Fill in allowed_mods.txt with the mods your server allows (guid=version, guid=* for any version, or ?guid=version for optional mods). Add cheat-tool names to signatures.txt.

Admin commands (server console, admins only)

kougp status                     connected players + verification state
kougp list                       current allowed mods + signatures
kougp reload                     reload config + lists and push to clients (no restart)
kougp allow add <guid> [ver]     add an allowed mod (also: remove)
kougp sig add <text>             add a cheat-tool signature (also: remove)
kougp kick <name> | ban <name>   manual moderation

Notes

• Admins are exempt — anyone on the server's adminlist.txt is never checked.
• Detections kick by default; bans are a manual admin action only.
• Optional Discord webhook posts a generic notice and admin/lifecycle events. Full detail is kept in a local violations.log for the admin.
• The server may run on Linux; client-side program checks are Windows-only.
• Like any client-reported system, a determined attacker who modifies the client can attempt to evade it. koumodgp raises the effort required; it is one layer of a server's defenses.