Looking for a DDoS detection tool

Looking for a DDoS detection tool

Hi,
I'm looking at using the Netflow Traffic Analyzer to alert us when there is an inbound DDoS attack against our network. Can anyone with experience with this product please advise if it's suitable for this purpose?  We have about 5 Gb of inbound traffic so it's important it can handle this (and more up to 10Gig) of netflow data.
Any help would be appreciated.
Luke 

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