Firewall

The Cloister Wraiths were, in the Twelfth Doctor's words, like the firewall of the Matrix. (TV: Hell Bent)

The Twelfth Doctor tricked King Hydroflax's body into connecting itself to all of the banks in the Andromeda Galaxy through the universal banking device. This also connected the computer to all of the banks' firewalls which began overloading it. Ramone later told the Doctor that it resulted in the computer being "deleted in a merger." (TV: The Husbands of River Song)