A leaked copy of the Harry Potter novel is not a national security threat in any way, shape or form. GCHQ are not there to enforce copyright.
No, but part of their remit is to protect "UK plc", from cybersecurity threats as they relate to economic attack.
J.K. Rowling was (arguably still is), a huge economic force. Billions and billions in revenues over many years, and she pays tax on all of it as a moral obligation: no Panama-led duck-outs into trust funds for her, so far.
So, let's suppose you're one of the 4,000-5,000 estimated staff members at GCHQ. You are looking at a part of the dark web in an effort to understand if its being used to arrange illegal arms deals, trade child pornography or other criminal material that falls within your employer's remit.
You notice a document that reports to be a leak of the publication of this book. It's about 500 pages, and the first page reads OK. You talk to your line manager about it.
You and your manager are going to have to realise that the leak of this book could lead to a loss in tax revenue equivalent to the entire annual operating budget of GCHQ. If genuine, it could be a severe impact on GDP.
Do you want them to do nothing? Or do you think it should be escalated internally and dealt with appropriately, which is to check with the publishers if it has been leaked?
The tricky question becomes what would have happened if the editor had confirmed it was real? What action would they have taken? That's where it gets dark...
On the side, they might try to stop this or that threat tl people's lives in UK or many eyes alliance. ;)
True. Good thing that GCHQ's mission is (and has always been) much broader than national security. For example, they have an arm which provides Information Security advice[1].
GCHQ are not there to enforce copyright.
Fire departments aren't there cats out of trees. This is a cat.
[1] http://www.gchq.gov.uk/what_we_do/Information_Security/Pages...
GCHQ is way out of line here. I am very concerned that the agency will eventually use these capabilities to blackmail our elected leaders. As much as I'd like to have leaders who aren't corrupt, we have what we have. I'd still not want our corrupt politicians to be slaves to shadowy organizations.