I have read that GPUs can be used in brute force attacks? But how can this be done and is there a need for any other hardware devices (hard disks for instance)?

Note: I'm more interested in web application security, but I don't want to put on blinders. I'm sorry if my question is ridiculous for you, but my hardware background isn't very good. I just know how basic components work together and how to combine them.

I'm choosing to assume you're asking why it's a risk rather than how to hack.

GPUs are very good at parallelising mathematical operations, which is the basis of both computer graphics and cryptography. Typically, the GPU is programmed using either CUDA or OpenCL. The reason they're good for brute-force attacks is that they're orders of magnitude faster than a CPU for certain operations - they aren't intrinisically smarter.

The same operations can be done on a CPU, they just take longer.
