A CCTV network, known colloquially as simply CCTV, was a specialised camera system used all over the universe to track people down. Sonic screwdrivers were capable of disabling the cameras. (TV: The Sound of Drums)
Though others felt demeaned by being under the watch of CCTV cameras, the Third Doctor once smiled waved at those guarding Stangmoor Prison excitedly, drawing their attention. (TV: The Mind of Evil)
The network gave the Saxon Master, under the guise of Prime Minister "Harold Saxon", access to all national surveillance cameras. He used those cameras to view the Tenth Doctor and his companions while speaking to them. The Doctor disabled the camera with his sonic, and they ran. (TV: The Sound of Drums) Matt Crane, under orders from Torchwood administrator Yvonne Hartman, used CCTV to locate who has been tampering with their "ghosts", both finding that (the Tenth Doctor) and, an added bonus, the Doctor's TARDIS, just as the Doctor was tracking them down. (TV: Army of Ghosts)
Park Vale Comprehensive School had a network of CCTV cameras, none of which picked up the October 2009 appearances of Odd Bob the Clown. (TV: The Day of the Clown)
In 2011, the Cybermen abducted humans from Colchester department store Sanderson & Grainger and teleported them to their crashed Cyber-ship. As the Eleventh Doctor quickly informed Craig Owens, they cunningly wiped the CCTV as well, leaving no trace of the disappearances. (TV: Closing Time)
A UNIT researcher used CCTV feed to find out how the Shakri cubes were affecting humanity at the end of the Year of the Slow Invasion: across the world, everyone near them had cardiac arrests. (TV: The Power of Three)
In 2020, Nasreen Chaudhry and Tony Mack used CCTV in their drilling project. When Mo Northover took over one night, the Silurians below the base began their attack and every CCTV camera was shut down. (TV: The Hungry Earth)
Far away from Earth, Peladon had a security system installed by Eckersley rather similar to CCTV. Cameras were stationed across the planet, and he monitored the activities of the peasants from the communications room. In the end, however, he was — in the words of Alpha Centauri — "betrayed by [his] own security system". Alpha and Sarah Jane Smith, through the visual and audio of the system, heard him conspiring with Ice Warrior Commander Azaxyr. (TV: The Monster of Peladon)
A prison ship holding a Minotaur recreated a 1980s Earth hotel, including its CCTV network. As Rita was about to be killed by the Minotaur, the Eleventh Doctor, in the surveillance room, switched off the system so as not to have to witness her death. (TV: The God Complex)
Used by Torchwood
The CCTV network gave Torchwood Three access to all the surveillance cameras in Cardiff. (TV: Day One) The camera images came up on the computer screens stationed all around the base. (TV: Day One, Meat, et al)
As well as around the city, the CCTV cameras were also posted inside of the Torchwood base itself, occasionally being used to monitor prisoners. (TV: Day One)
Occasionally, members of the Torchwood team used the CCTV cameras to watch people for personal reasons, such as when Jack Harkness watched Gwen Cooper kiss her fiancé Rhys Williams. (TV: Meat)
The cameras were sometimes shut down, such as when Weevils were being kidnapped. (TV: Combat)