A channel with 18,000 subscribers was holding 11% ERR consistently. Then it dropped to 7.8% in one week — same content, no complaints, nothing obvious. Turned out 600 bot accounts had joined over three nights and never opened a single post.
What spam bots actually cost you
Telegram calculates engagement rate as a share of your total subscriber count. Every 200 inactive bot accounts in a 10,000-subscriber channel costs you roughly 2% ERR. At 1,000 bots that's 10% gone — silently, without any notification.
Ad buyers check ERR before placing orders. A visible drop with no explanation creates doubt that doesn't go away just because you cleaned the bots out later. The reputation damage outlasts the attack.
Bots arrive in two ways. The first is a targeted attack: a competitor pays a service $3–5 per thousand ghost subscribers. The second is passive — your channel ends up in traffic reseller databases and starts receiving accounts from shared pools.
How TGuard identifies spam bots
TGuard maintains a collective database across all connected channels. Every time an admin bans a user — manually or through automation — it's recorded. An account banned in five or more channels in the network gets marked as a known attacker.
This is documented ban history, not behavioral profiling. Five independent admins in different channels all decided this account was a problem. That's a pattern, not a coincidence.
When the antivirus fires
TGuard tracks how many known attackers join your channel within a one-hour window. When three or more show up in that window, the channel owner gets an alert.
The alert includes the exact count of suspicious accounts and the list of invite links they used to get in. If the attack came through multiple links, all of them are listed — so you immediately know which ones to revoke.
Auto-ban vs. notify-only
By default, the antivirus notifies and leaves the rest to you. You can enable automatic blocking: when the threshold is hit, TGuard bans all confirmed attackers in that batch without waiting for your input.
Regular subscribers aren't affected. Only accounts from the attacker database get banned. Like any antivirus, there's a small false positive rate — about 1–2%.
Users who solved your channel's captcha are excluded from the check — even if their account appears in the attacker database.
Works for join requests too
If your channel uses join requests instead of open subscriptions, the antivirus adapts. TGuard auto-rejects requests from known attackers before they ever enter your subscriber list — the bot doesn't just get removed, it never gets in.
Why this catches what captcha misses
Captcha is effective against cheap bots that can't interact with a button. Professional attacks use "aged" accounts — ones with real activity history and a normal-looking profile. They pass captcha without any trouble.
TGuard identifies these accounts through their ban history across the network, not their behavior at the door. Even if an attacker passed your captcha, the network database already has their record from five other channels.
How to enable it
- Open @channel_guardian_bot and select your channel.
- Go to Security.
- Find Antivirus and turn it on.
- Optionally, enable automatic blocking to have attackers banned without manual action.