Dear F1 friends in the USA

I have an F1 visa and will be graduating in June 2009. Since I was awarded full scholarship by my school I make an agreement with them not to work outside campus. Currently I work on campus 20 hours a week and the school pays me accordingly. However, with the needs back home I need to work more hours and recently someone is offering me job without work permit. They told me I need to give them only my Social Security Number and they will pay me by check. My fear is… is it safe to work with out work permit? Is it a good idea use SSN for the job opening? In my SSN it also says that I m not allow for work. As far as I know F1 students are not allow work more then 20 hour in week. I do not understand this policy because  I know some friends who are working more then 20 hour in week without work permit and they are paid by check as well. Will they have trouble later? Please fell free and shared your experiences. I am sure some of you guy know very well about it. Would be grateful for your sharing about it.

Thanks