DEET is the active ingredient, not a brand name. DEET stands for N,N-diethyl-meta-toluamide. It is in most insect repellents. If you want to learn more about it try these sites:
www.epa.gov/pesticides/citizens/deet.htm
www.cs.princeton.edu/~jlk/deet/
www.deet.com
and many more.