How they work
Sonar 2 sends each new player to a lightweight fake server and checks gravity, block collisions, vehicle packets and the protocol. A real client passes in a moment; a simple bot fails. It stops bots no matter where they come from, but it does not care whether a real person is on a VPN.
Kordon looks at the address of every login within the plan's daily limit, and of every login during an attack: VPN, proxy, Tor, hosting, residential proxy, and where the wave of joins comes from. When a bot wave starts, it switches the server to attack mode and closes the networks the bots use. A banned player on a VPN is stopped too. A bot from a clean home address is not.
Does Sonar block VPNs?
Sonar 2, the free plugin, does not check VPNs or proxies at all: a real player behind a VPN passes its verification like anyone else. VPN, proxy and Tor blocking is part of Sonar 3.0, the paid hosted version, together with country rules.
So if you are looking for a Sonar AntiVPN, there are two ways: move to Sonar 3.0, or keep the free Sonar 2 and add a separate AntiVPN on the same proxy, such as Kordon.
Side by side
| Kordon | Sonar 2 | Sonar 3.0 | |
|---|---|---|---|
| Type | Hosted service | Plugin | Hosted service |
| Price | Free plan, paid from $4.99/month per server | Free, GPL-3.0 | From €5/month, no free plan |
| Limits | Checks per day per server | None | Servers and player count per plan |
| Verification world | No | Yes | Yes, plus web CAPTCHA |
| VPN and proxy blocking | Yes | No | Yes |
| Country rules | Yes, from Basic | No | Yes |
| Nickname and version rules | Yes, nicknames from Basic, versions from Pro | No | Not described |
| Panel | Yes | No | Yes |
| Platforms | BungeeCord, Waterfall, Velocity | Velocity, BungeeCord, Paper, Spigot, Folia | Velocity, BungeeCord, Paper 1.21+ |
Running Sonar and Kordon together
The two do not get in each other's way. Kordon decides at login whether the address may join at all; Sonar then verifies the players that got through. Many bot attacks come through proxy lists, so Kordon removes most of a wave before Sonar has to deal with it, and Sonar catches what comes from clean addresses.
If you are thinking about Sonar 3.0 mainly for its VPN blocking, compare the limits: Sonar 3.0 plans are sized by servers and players, Kordon plans by daily checks per server, and Kordon has a free plan to try it on.
Getting started
Put Kordon on the same proxy as Sonar and leave it in observe mode for a day or two. In observe mode Kordon lets in the players it would block for VPN, proxy or country and records them; your blacklist, nickname and version rules and Kordon's own blocks still apply, and during a bot attack the server is protected for real. See installation on Velocity and the overview of anti-bot plugins.