Spam Vanquisher

Discord bot that prevents automated message spam on the server. The bot works by monitoring the messages in the server's channels following preset rules. When a rule is triggered an action is taken against the bad actor. Disabling communications and banning is supported but the set of actions can be expanded by placing new files in src/actions folder (more on extending below).

The bot also supports slash commands for manual ban and adds a new context menu button for messages to manually remove messages that might have slipped the automatic detection. (These features are currently designed with testing out the automatic measures in mind and commands will only work for the server's administrator and the bot administrator)

Concept

The most basic idea of how it can be used is to monitor the members' messaging activity throughout the server. If an actor posts X amount of messages across Y amount of channels in Z seconds it is most likely an automated behavior (the default baseline is 4 messages across 4 channels in 20 seconds) so the bot takes action (ban by default).

It can also monitor the message contents preventing flood of identical messages or messages that match a certain regex (a link by default).

Setting up

Create a new bot at Discord Developer Portal. I recommend setting the bot as private. This bot was designed to be running on one server at a time although it can monitor several servers at once.
The permissions to grant the bot depend on what it will be used for. In general it needs Use Application Commands, Read Messages, Send Messages, Manage Messages and a set of moderation permissions depending on what you have in mind (ban/kick/timeout members). By default it's initialized with MESSAGE_CONTENT intent but if you're not planning to use content filter and only monitor the message frequency you may remove GatewayIntentBits.MessageContent from client in src/client.js
After the bot on the discord side is all set up it's time to launch the project. Run

yarn

in the project's directory to install all dependencies.

Create .env file in the root folder with your bot's credentials. Use .env.example as a guide, all the values can be found in your bot's application page at Discord Developer Portal.
Set up a config.json in the root folder. If this is the first time you run the bot and you don't have a config.json one will be automatically created based on src/config.default.js. You can tweak that file before running the bot to get the config.json that is to your liking.

Usage

Run the bot as a service with pm2.

npm install -g pm2
pm2 start index.js
pm2 startup # follow instructions it provides
pm2 save

This ensures the bot is restarted in case a crash occures and the service is started when the server itself is rebooted (e.g. in case of an outage).

Extending

New commands can be added to src/commands folder. As long as they extend DiscordCommand class they will be automatically registered and hooked up.

Same goes for new actions: put them in src/actions and extend Action class. The obvious contender for that would be kick.js.

Persistence considerations

The bot keeps its store completely in memory. Given the relatively short span of relevant data (default TTL is only 30 seconds) there is no need for constant writes to the disk. In an unlikely event of a reset you only lose up to 30 seconds worth of data. If that seems unacceptable you can extend store object in src/store/index.js to facilitate lowdb which is already used to handle config.json.