They are effectively a staffing agency focused on technical positions and security clearances. They staff roles almost entirely for the government on an as needed basis when there isn't enough experienced engineers/physicists/software developers for a particular project.
Consequently, the systems they build are whatever is a government priority at the time. Right now, the 3 letter agencies are spending big on "Cyber" so Mitre is building a lot of cyber related systems. https://attack.mitre.org/ is one of their interesting recent projects that is public facing.
Mitre does seem to treat their own employees very well. I've had mixed results working with them, but not really any worse than any other government staffing company.
Consequently, the systems they build are whatever is a government priority at the time. Right now, the 3 letter agencies are spending big on "Cyber" so Mitre is building a lot of cyber related systems. https://attack.mitre.org/ is one of their interesting recent projects that is public facing.
Mitre does seem to treat their own employees very well. I've had mixed results working with them, but not really any worse than any other government staffing company.