As others have said, also its sequel Rule 34. It's been a while since I read these, but I don't recall anything in there that jumped out at me as "you can't get there from here."
There was originally supposed to be a third novel in this series, but Stross cancelled it[0] after Edward Snowden.
"Halting State" wasn't intended to be predictive when I started writing it in 2006. Trouble is, about the only parts that haven't happened yet are Scottish Independence and the use of actual quantum computers for cracking public key encryption (and there's a big fat question mark over the latter—what else are the NSA up to?).
I'm throwing in the towel. I probably will write another near-future Scottish police procedural by and by, but it won't be a sequel to the first two except in the loosest sense. The science fictional universe of "Halting State" and "Rule 34" is teetering on the edge of turning into reality. Meanwhile, the financial crisis of 2007 forced me back to the drawing board for "Rule 34"; the Snowden revelations have systematically trashed all my ideas for the third book.
