Does a former company need my social security number for tax purposes and why?

I worked for a company since 2010, paid as a contractor. I filled out w9 forms for them, but now after I have left. They had sued a company I owe to try to shut it down and were unsuccessful. They now are asking everyone - but me - for my social security number with the statement they need it for taxes. They are using their lawyers to try to get the information from everyone - but still have not contacted me. Personally, I think they want to do something shady. Since I have filled it out in the past, and they have reported taxes since 2010, I feel I am not required to provide them any further information. I do not receive any money from them anymore and I report my taxes properly. How should I handle this without giving them my social again - I think they are being shady, and besides, if they properly reported taxes in the past, they should have my number on file.