I'm currently researching what malicious activities can one do with a computer containing a high-end GPU. So far the only uses I found were Bitcoin mining and password cracking. Are there any other possible malicious uses for such computers?
A high-end GPU makes it very easy to do any sort of computational process that can be highly parallelized, each individual process doesn't need a lot of memory, and requires similar operations to be done to differing starting input.
So if you have md5 hashes with salts that you want to find the password that goes with, its trivial; e.g., generate a simple scheme to feed the GPU billions of passwords per second to try simultaneously and compare to the hashes you have. You could also do things like try constructing hash rainbow tables as well.
Another good candidate would be brute-forcing decryption of a file that's encrypted with a strong cipher. A GPU could plausibly be used to parallelize the process of doing trial decryption under many candidate passphrases.
I wouldn't say bitcoin mining is malicious; its basically the intended method of generating currency (except a GPU makes it more efficient).
Off the top of my head could also use a GPU to better crack simple CAPTCHAs using computer vision techniques.
Here are some other examples (some of these are vulnerabilities of GPUs):
- running stealthy malware,
- denial of service attacks (since WebGL allows browsers to use GPUs for accelerating webpage-rendering, if user opens a malicious website, his GPU can be overloaded such that it never responds and thus, crashes)
- extracting credit card numbers, email contents and classified documents from remanent data in GPU memory
- leaking other users' data in cloud-computing.
- Here is a real incident which happened in 2013: A malicious person hid a bitcoin miner in ESEA (a video game service) software. This miner used the GPUs in users’ machines for mining bitcoin without their knowledge. The miner overheated and harmed the machines by overloading the GPUs. Thus, the malicious person earned cryptocurrency at the expense of the users’ resources.
See my survey paper for a more detailed discussion on security vulnerabilities of GPUs along with their countermeasures, and works which show use of GPU for malicious purposes.