customizing/identifying spam mails

[WalyBaly]

is there any way i can tell spamassassin to identify certain mails of 
spam type based on below conditions :

it could be either
source/from:
subject:
body:
ip:
if any of the contents of the above tags are present, the same should be 
identified as spam.

for eg.
of body contains word
PORN
the same mail should be identified as Spam
rgds,
waly