The latest modification on the reference client that should fight the
DDoS could be also implemented on libbitcoin:

Add HasCanonicalPushes(), and use it in IsStandardTx
https://github.com/bitcoin/bitcoin/commit/87fe71e1fc810ee120a10063fdd26c3245686d54

Add option to avoid spending unconfirmed change
https://github.com/bitcoin/bitcoin/commit/1bbca249b202c4802cc2c4d4de4a26e6392b4d92

Grazcoin

On 02/14/2014 09:34 AM, Grazcoin wrote:
> How about ignoring all non-standard transaction (e.g. with outputs
> smaller than dust limit 5430 satohis)?
> We could still keep an option to enable the non-standard transactions
> using a command line argument.
>
> On reference implementation since 0.8.2:
>
> https://bitcointalk.org/index.php?topic=219504.0
>
> Payments (transaction outputs) of 0.543 times the minimum relay fee
> (0.00005430 BTC) are now considered 'non-standard', because storing them
> costs the network more than they are worth and spending them will
> usually cost their owner more in transaction fees than they are worth.
>
> Non-standard transactions are not relayed across the network, are not
> included in blocks by most miners, and will not show up in your wallet
> until they are included in a block.
>
>
> On 02/14/2014 07:57 AM, Amir Taaki wrote:
>> Hey, you're right. What rules do you propose that are elegant that we
>> can use to prioritise transactions and filter spam? I don't believe the
>> mempool rules in Satoshi bitcoind are well designed.
>>
>> On 13/02/14 22:41, Grazcoin wrote:
>>>
>>> The transaction:
>>> c5e2814507f49b5370f70c4477b02854a34c16af2c301cf097d1a634c4721ee6
>>> is an example for a spam transaction (part of the attack on bitcoin
>>> network).
>>>

>>> $ sx fetch-transaction
>>> c5e2814507f49b5370f70c4477b02854a34c16af2c301cf097d1a634c4721ee6 | wc
>>>       1       1   51317

>>>
>>> $ sx fetch-transaction
>>> c5e2814507f49b5370f70c4477b02854a34c16af2c301cf097d1a634c4721ee6 | sx
>>> showtx | head -n 20
>>> hash: c5e2814507f49b5370f70c4477b02854a34c16af2c301cf097d1a634c4721ee6
>>> version: 1
>>> locktime: 0
>>> Input:
>>> previous output:
>>> 9d9dd3402bb4ad7c409f3b5cf1b695a2d7815a58ef12982d0aeaa6a6a6880aee:0
>>> script: [
>>> 30450221008eb4a4a7d91468fa1ec083dd72868dd0ccb314df580e0a84e76b51df43c58ae402205d07ddf588ee43bd4780ba9241c7075ec46cc1e83c9d21e4c49e3a01aefa516701
>>> ] [
>>> 045cce731a4d6308e5baf7d73ad2fcab298563bbc86404905d84e2b0ec314946a6d0e8076bd9db8e85ca0e7e5bd33f2adc629d48ac26f10e6ee459fc64efb5b8f5
>>> ]
>>> sequence: 4294967295
>>> address: 1SochiWwFFySPjQoi2biVftXn8NRPCSQC
>>> Output:
>>> value: 1
>>> script: dup hash160 [ addd9328c13df98785d28be84ea8b93af1777969 ]
>>> equalverify checksig
>>> address: 1GrKLUduDbS5WM8zMJ4qzPCZ7UMpxj9AMo
>>> Output:
>>> value: 1
>>> script: dup hash160 [ 5754bc1d08e76b8c021d7e04c7448ab751df5dad ]
>>> equalverify checksig
>>> address: 18xmJAisJ1GBLVpuyFmqaA7LNmj8d6NE73
>>> Output:
>>> value: 1
>>> script: dup hash160 [ ad731d73d79a753ae71d64aa80c7697ee7cd603f ]
>>> equalverify checksig
>>> address: 1Gp7oXBtT2V5a4gqGcDVetw2aPw7vFPx1D
>>>
>>> It just sends 1 satoshi to a long list of addresses, and it is clear
>>> that it will never get included in a block.
>>> Shouldn't we just ignore the tx (not keep it in the memory pool and not
>>> forward it)?
>>> blockchain.info does.
>>>
>>> If for some reason it does enter a block, we'll get it anyway.
>>> Grazcoin
>>>
>>>
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