Reach

In survival you can reach an opponent from 3 blocks away, measured from your eyes to their hitbox. Reach adds anything from a few tenths of a block to a couple of blocks on top. Blatant reach gets spotted instantly, so experienced cheaters add very little.

Even half a block decides trades: whoever lands the first hit knocks the opponent back and gets the first hit again, while the replies fall short. In sumo, duels and bridge fights that's a string of free hits; on anarchy and in BedWars it's a fight the honest player lost without ever understanding why.

• The opponent takes damage while the gap between the players is clearly over three blocks
• The cheater almost always wins the first hit, and return hits never reach them
• Hits opponents who have already jumped back or stepped off an edge
• Mind the ping: on the victim's screen the attacker lags behind, so “he hits me from five blocks” isn't proof on its own

Distance can't be measured from the server's current positions: the attacker saw the target where it was, shifted by their ping. So the anticheat keeps the target's recent positions, uses the client's replies to marker packets to tell which one the player had seen, and casts a ray from the eyes along the sent rotation to that hitbox. Beyond 3 blocks plus a small tolerance is evidence.

The tolerance swallows the extra tenths, so subtle reach is caught by repetition: honest players land a borderline hit now and then, cheaters land them every fight. DGuard bans only after 400 points of evidence across three separate episodes.