webform with captcha 模組還是招架不住spam

hi,
小弟有使用webform去做消費者詢價的功能，不過受到spam的影響，所以不得不安裝captcha module去做控管，不過未料還是被攻擊了 >"<

底下是被po的內容

Submitted on 07/17/2007 - 17:55
Submitted by anonymous user: [152.7.198.180]

Submitted values are:
姓名/公司行號: ccvdvcxv
聯絡電話: ccvdvcxv
聯絡住址: ccvdvcxv
電子信箱: ccvdvcxv
您感興趣的產品:
brother mario polyphonic ringtones theme protected White theysend ringtones the Focalysts youraguilera christina ringtones and part theringtones code be a thereanime download ringtones to are infabolous ringtones the said ofcell phone redneck ringtones with in ofheavy metal ringtones targeting. families trivialcell phone redneck ringtones being Drum overnotre dame fight song ringtones it has Alaskanrilo kiley ringtones stuck theasian ringtones major recent specificfree samsung a700 ringtones city a entertainmentmovie ringtones tv the taken trust.free phone ringtones send venue resulting Cabinfree country ringtones August Amsterdam couples,download alltel ringtones

請輸入送出表單提示: ccvdvcxv

很明顯的captcha沒輸入答案就被po文了"請輸入送出表單提示: ccvdvcxv"
spam應該是利用程式的bug攻擊的吧
我有試過spam模組，不過不對webform做過濾，我翻到的資料好像也只有captcha能夠協助webform不受spam攻擊，如今也失守了，請教一下還有什麼更好的方式對付spam嗎?