Bad Wolf virus

The Bad Wolf computer virus erased all information on Rose Tyler from the Torchwood Institute database. (TV: Love & Monsters) This was a result of Rose, as the Bad Wolf entity, scattering the phrase Bad Wolf throughout space and time. (TV: The Parting of the Ways)

It is possible that Torchwood reprogramed this Virus and used it to erase all references of Torchwood on the Internet. (TV:  The New World)