Infested Mossy Stone Brick are a variant of stone bricks that conceal silverfish, which emerge when the block is broken without Silk Touch. They appear identical to regular mossy stone bricks but take significantly less time to break. When a silverfish is attacked nearby, other hidden silverfish in surrounding infested blocks emerge to attack the player. Infested Mossy Stone Brick cannot be obtained in item form and are only available through the Creative inventory or commands.

They generate naturally in igloo basements but are not found in strongholds, unlike regular infested stone bricks.

When mined with any tool, except one enchanted with Silk Touch, an Infested Mossy Stone Brick block releases a silverfish that immediately attacks. Infested blocks take half the time to break compared to their normal counterparts, making them identifiable when mined. In Java Edition, they can also be distinguished using the debug screen. In Bedrock Edition, placing a note block on an Infested Mossy Stone Brick block produces a flute sound, while regular mossy stone bricks produce a bass drum sound.