New Edit for 2026
We took this down in favor of other announcements late last year, as we only get 2 slots. It's back now because we've had a resurgence of this type of post.
Do not post about offline mode servers. Do not recommend software or plugins that help run one. You will be banned. Read the Admincraft Policy section at the bottom.
Thank you.
Hey there, REPO here. We get questions like this a LOT, so I'm trying something new. Please read the below before posting a thread like this.
"How did this person find my server!?!?!?!?!"
There are few enough IPv4 addresses that a simple bot made with ChatGPT and zero skill can scan the entire internet for Port 25565 in like 30 minutes. There are HUNDREDS of bots out there that do this 24/7/365. Some of them are benevolent (such as bots like matscan that warn people if their servers are dangerously insecure), some are neutral (like ServerScannerV2 which just accumulates data for their website project), and some are malicious and trying to grief servers.
"How do I make them stop?"
You don't. They will keep doing it forever. Most non-malicious bots will log into your server once, or sometimes once per some time interval, and then stop. Others that are coded poorly will be more persistent. And then the malicious ones will keep checking back continually.
If your server is secure but it still bothers you to see, you can add the source IP address to your firewall to prevent the connection. Some non-malicious bots will also have a website or Discord where you can request your server to be skipped.
"Is this dangerous?"
Nope. Not if your server is secured. There are no known exploits in Minecraft that allow a server scanning bot to run code on your host or escalate their privileges. The last time we had that was in 2022 with the Log4J exploit, which was quickly patched, even by Mojang. If you aren't deliberately using an old minor patch of Minecraft, you're fine.
"How did they log in as me / Herobrine?"
(Note: If you only see a name like that instantly disconnecting, skip to the next section. This only applies if they actually appear in game.)
Your server is running in Offline Mode, which is a config option in the server.properties that is intended only for use on a home LAN that is not connected to the internet. Most people use this feature to avoid having to buy a license for Minecraft, aka "cracked accounts". Please be aware that this is illegal and is considered software piracy by most governments.
Minecraft servers send information about the server to players on the server list, including a partial list of currently logged in users. You can disable this "feature" in the server.properties file by setting hide-online-players=true. Malicious bots typically sit and watch a server for a while, gathering a list of players over some amount of time, assuming that if the server is in Offline Mode, one or more of those players will have Operator permissions. They then log in as all users in rapid succession until they find one that does, and use the Operator permissions to grief your server.
"I see a player disconnecting but never connecting! How are they doing that?"
It's just a bot using an offline mode account. It is only showing as Disconnecting because it is getting filtered by the security systems you have in place AFTER the server knows that it is trying to connect, but BEFORE it actually does. Showing the Disconnected message is just the server's way of informing you that the login attempt was rejected. Nothing to worry about. You can ignore it.
"My server got griefed, what do I do?"
You restore from backup, secure your server, and move on. The groups that do this are doing it for amusement and power fantasy. Some of them insist that you can request a world backup from their Discord, but the whole point of that is to mock you and make you beg for their mercy. They might actually give it to you, I don't know.
"How do I secure my server?"
You set Online Mode to true in the server.properties and run a whitelist. That's it. Those 2 options are 100% effective at preventing unwanted people from gaining access to your server. You do not need to do anything else whatsoever to be secure, but you can optionally change your server's port from 25565 to any other unassigned port. This will make it much slower for server scanners to find your server, as most are lazy and don't check non-standard ports. Note that this only reduces the odds of a server scanner finding you; it does not make you more secure.
Additionally, having automatically executed, scheduled backups running at predictable intervals is an excellent idea just in case something goes wrong. Ensure that you periodically verify that your backups are usable by doing a test restore on another machine, as a backup solution that has never been tested is basically worthless.
Finally, a block logging plugin such as Prism (V3 stable Download | Github) (V4 alpha Download | Github) is recommended, as it allows you as the Admin to roll back individual unwanted changes without doing a full backup restoration.
Admincraft Policy
If your post contains any information that indicates that you are running an Offline Mode server, your post will be removed and you will be banned for 28 days for your first offense.
Additionally, suggesting methods for a user to continue running an Offline Mode server "safely" will earn a 7 day ban for commenters. This includes whatever plugin or launcher you're wondering about right now as you read this.
Admincraft is in active communication with Mojang Intellectual Property Enforcement, the team within Mojang that actively hunts down servers and other individuals and groups that are breaking their EULA and MUG. They watch here regularly, and if we do not enforce this, there is a nonzero chance that Mojang, Microsoft, or Reddit would shut down our subreddit. Keeping the subreddit open for everyone for the long run is the priority. We cannot and will not support Offline Mode servers.
The only times when discussing an Offline Mode server is allowed are when you clearly state that your server is not accessible to the internet and that all players have a legal Minecraft account, or when it is behind an Online Mode proxy, such as Velocity.
This post
Please use the comments here to suggest additions to this FAQ/guide, and to ask clarifying questions about Admincraft policies and security best practices. Do not state or imply that you are currently running an Offline Mode server.