from random import randint

ddosed = 0
notddosed = 0
for a in range(1, 100000): # let's do 100000 samples
	selected_an_attacker = False
	for b in range(0, 10): #select ten masternodes
		if randint(0,1000) >= 990: #last ten are attackers
			selected_an_attacker = True

	if selected_an_attacker:
		ddosed += 1
	else:
		notddosed += 1


print ddosed, notddosed

---- output ---
10588 89411
10443 89556
10481 89518
10460 89539
10502 89497
10475 89524
10528 89471