Is Infected Vermin legal in Standard, Modern, and Commander?

Infected Vermin is legal in: Legacy, Vintage, Commander.

What type of card is Infected Vermin?

Infected Vermin is a Creature — Rat. Its oracle text reads: "{2}{B}: This creature deals 1 damage to each creature and each player. Threshold — {3}{B}: This creature deals 3 damage to each creature and each player. Activate only if seven or more cards are in your graveyard. Power/Toughness: 1/1"