There are two risks to be mitigated:
- Someone removing something from your bag
- Someone adding something to you bag
I expect the first is by far the most commonly experienced by travellers. In fact, I can only think of one case where it has been claimed the second was the case.
My first mitigation for the first point is not to carry anything in my checked luggage that is not easily replaced by my travel insurance, or of no consequence to me if it does go missing.
The second is such a rare case that it is difficult to know how much effort the mitigation should require.
The only time I have had a problem with things going missing was when my bag arrived delayed (and hence unaccompanied) into KBP (Kiev). The things that went missing were a large bottle of shampoo, two bags of Caramello Koalas and a pack of 20 clip-on Koala toys we were taking as gifts. All up about $10 in value. Disappointing, but not a major loss.
For travel through the USA, I just use cable ties. Once the TSA has cut one to get inside (they left a note to say they had inspected it) and they then locked my bag using a padlock that was left inside one of the small pockets. Its a good thing they also left the key in the unlocked pocket so I could unlock it once I received the bag. I was very surprised to see my bag locked with my own padlock that I had not installed!
I also make sure that when I pack my bag there is nothing that will likely raise suspicion during an x-ray. That means I put things like cables (I carry a few network cables with me on most trips) in an outside pocket and not in the main body of the bag. My bag usually only contains clothes - and maybe the odd pack of Tim Tams

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