I applied in-person. I interviewed at OPSWAT (San Francisco, CA) in Mar 2015
Interview
1st phone interview asking about the project I list on my resume
2nd asked to do a small project
1st in-person interview with 2 engineers, they asked some technique questions
2nd in-person interview with a senior manager, question are more liking checking personality, not very technical
I applied in-person. The process took 1 week. I interviewed at OPSWAT (San Francisco, CA) in Apr 2016
Interview
Nice people there. I did not get the job. I was asked to write a program to find a file. It turned out more complex than expected. Need to create your own file system and the best data structure. Only did pseudo code on the white wall board for an hour. You can pick any language. I did it at home for fun. Now I now how to make viruses. Good luck