udpflood attack !

["Liuhy" <solar_liu () fescomail net>]

Hello, everyone,

I am a newbie in using snort, I have a question to ask:

I used an application named "udpflood.exe" which send udp packet to the host that snort is running, and 
I don't change the snort.conf file. But snort cann't find this attack, don't give any alert in alert file. 

Why? 

Thanks and regards!
Liuhy