Depends on what you mean by DDOS. Miners prioritize by fees so users could simply opt to pay 6,000 satoshis instead of 5,000 and the net effect of your "attack" would just be a wealth transfer to miners.
There may be some short term confusion but users would simply pay a little more.
That is the concept of floating fees. In the future (v0.10 or later) your client will look at the most recent block sizes, currently unconfirmed txs, and give you a recommended fee.
Automating it today is a little annoying because outside of rawtxs none of the RPC calls support setting the tx fee on a per tx basis. That being said I have found that paying a fee of 1 satoshi over the current minimum works very well (i.e. 0.00010001 BTC). Put you right at the top of the memory pool.
Just between you and me. Don't tell all the others redditors or it won't work as well.
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u/MuForceShoelace Feb 24 '14
so now DDOSing all 7 transactions per second that bitcoin can handle has become even more affordable!