Rank
#1	Gravity Forms Zero Spam	97	5	2		4
#2	Forget Spam Comment	95	12	1		2
#3	Antispam Bee	90	29		4	9
#4	IP Ban	82	47	14	1	5
#5	Spam Destroyer	79	50	23		27
#6	ALTCHA Spam Protection	77	63	11		44
#7	Stop Spammers Classic	72	90	9	6	1
#8	WP Armour – Honeypot Anti Spam	69	92	22		7
#9	La Sentinelle antispam	60	124	11	1	2
#10	Email Encoder – Protect Email Addresses and Phone Numbers	52	132	33	2	102

Plugins tagged anti-spam