Central London will be targeted by a mock cyber-terrorist attack in March, as part of a campaign to find the next generation of cybersecurity workers.
The exercise will mark the end to a yearlong contest held across the UK, designed by the GCHQ and the NCA alongside a coalition of networking and defence firms.
Stephanie Daman, chief executive of Cyber Security Challenge UK, said: "This is the largest collection of cyber expertise we have ever pulled together to put our candidates through their paces.
"With an emphasis on realistic operational environments and demands, this year’s finalists will face a master class that will excite and challenge in equal measure."
Qualifiers for the final are ongoing, with openings still available for interested parties looking to join the 18,000 who have already signed up to compete for the 42 places in the last round, where they will be assessed on technical, interpersonal and decision-making skills.
Winners will receive a mix of university bursaries, accreditation, and internships, joining the 100 who have already passed through the programme into employment in the industry.
Mark Hughes, chief executive of BT Security, one of the firms behind the contest, said: "As the UK faces a worrying shortage of cyber security talent, every new reported threat raises our susceptibility to being attacked.
"As a result it is a critical matter of national security as well as economic prosperity that we ensure the right people are found, trained and ready to take on key roles in the cybersecurity profession."