Generally, there is a very low barrier to entry when it comes to software or network-based attacks due to the fact that actual costs are minimal and most resources are readily available. This does mean that it's generally much easier to attack the software of a system than the hardware, but unfortunately that also leads to overconfidence in, as well as misplaced trust in hardware.
There is a clear 'hierarchy of attacks' in the hardware world. There are costs, often significant, involved in acquiring your hardware 'target' which might be damaged or destroyed in the process. There are a number of useful tools that cost anywhere from a few dollars to a few million dollars. I'll give a couple examples of what's possible within budgets of $100, $10,000, and $1,000,000. I'll point out how many capabilities are much more accessible than most assume, and how vulnerable to sub-$100 attacks most of our 'secure' hardware really is.
View the slides
.