Fuel is leaking at the back of fuel filter by the drain valve on my 2002 ford f350 7.3 diesel motor

Have u tried checking to see if the fuel filter is tight? Or perhalps the valve is cracked or damaged

Possibly one of the rubber seals has perished ? If you have not changed the fuel filter for sometime/ever, fit a new one ( always worth the cost ) it will come with new seals ( put a coating of oil on seals before fitting ). Tighten to Ford filter spec only, an over tight filter can leak just as bad as a loose filter.