Make it into a game of Solitaire, with some changes
FYI, I have no experience with LARPing, and haven't utilized a system like this in real life. I do have some experience with designing simple games.
Make sure each ref has a deck of cards, and each challenge a game of solitaire with a specific requirement needed to make. To speed things up, add random elements like stating that, for this round, suits don't matter, or the value of a face card is interchangeable with any other face card. Harder challenges require all the cards to be used (like a normal game of Solitaire), where easier challenges only require a single stack to be completed.
For when a hacker is having difficulty, always have the "brute force" timer available, when their "backup system" gets past the issues and the hack succeeds anyway, but this should always be longer than ideal. Base these as being slightly longer than what the existing system uses for a timer. So if it takes one of your current challenges 5 minutes of hacking, the solitaire system should be about 7 minutes for the brute force method.
If you need to balance it out, have two specific timers ready, one for the maximum time it should take for the challenge to complete (the brute force option), and one to prevent too early of access because of a lack of balancing the system (which is 5 minutes earlier than the brute force option).
Meaning that player decision making can only change things within a 5 minute time range. If they beat it too early, they won't break the event because they're super smart, and will have to wait for the minimal timer (say it's a catch up timer as their system is catching up to their fast programming). If they're too slow, the brute force system will solve it for them.
If they succeed before the brute force timer, they get to memorize one of the system's "loopholes" (the random rules used to modify the game) and can use it on a future hacking challenge.
Only one loophole can be saved this way, and each loophole can only be used once. After it is used, and the player succeeds on the new challenge, they may not keep the loophole they just used.
To add to the ominous feel and the tension, write the special rules on individual note cards. When a player encounters a hacking challenge, the ref simply hands the player the deck of cards and the note cards of special rules relevant to this challenge.
I suggested this as it does follow some trends of working a computer system in real life.
You can teach yourself all of the basics and practice, practice,
practice, but you will always find things that surprise you.
Its strength and difficulty isn't always reliant on outside sources
but usually dependent on you, which is why I chose Solitaire as the
tool of choice.
It isn't always about being the best or most thorough, it's often
about finding the one abstract way that makes you succeed, and this
version of Solitaire provides this via the abstract rulings.
Last, but not least, you often find trends in systems that are
noticeable in similar systems, and you may base a solution from one
event from something you found in another, and the concept of
"remembering" a loophole in my example utilizes this kind of idea.