Is spectraforce.com Safe?

Out of nowhere, I have received several calls from SpectraForce while using some supposedly unrelated job search sites. SpectraForce was clearly promoted in many email signatures that I have received which is why I'm commenting here. The jobs I have received from them do seem legitimate but before even getting an interview or job offer, I was asked for my SS# - after I refused to supply it without a job offer / in-person interview, I was told that the job consideration could not be continued without providing it. After some research I learned that this is not info that should be required (in the USA) unless an in-person interview or job offer has already occurred. Most of them email or call me about jobs which are scattered around the entire USA and they have a very thick foreign accent. Some of these jobs are literally on the exact opposite side of the USA - quite literally I would have to travel from Maine to southern CA for the job. I would be cautious about this company.