MediaGuard 3 (sometimes refered to as SECA 3) is a Conditional Access System that replaces the two prior generations, MediaGuard 1 and MediaGuard 2. Throughout 2008, broadcasters switched to MediaGuard 3 (some kept broadcasting in simulcrypt with MediaGuard 2 or Irdeto) in a step up of security, as MediaGuard 2 is considered at least partially compromised at this point. MediaGuard 1, the first generation, had been broken in the late '90s, resulting in a bitter legal dispute with NDS over allegedly financing the cracking operation.
A few years later, MediaGuard 2 was also at least partially broken. Card swap-outs are generally required for upgrades to the system.