Automatic heuristic driven prioritization, with sane defaults and some configurable knobs, is exactly what I suggest.

In the short-term though, any connection limits added to the client by default would be the simplest and easiest protection measure to audit.  It would improve things a lot over the current situation where there are no limits, and it requires no manual intervention from node operators.

Warren







On Fri, Aug 16, 2013 at 3:46 AM, Mike Hearn <mike@plan99.net> wrote:
A ban-subnet RPC would be a reasonable addition, but obviously DoS attackers that are IP or bandwidth constrained are really just script kiddies. Also anything that involves every node operator doing manual intervention rather works against decentralisation and having a big network. That's why I keep pushing for automated heuristic driven prioritisation.


On Fri, Aug 16, 2013 at 3:41 PM, Warren Togami Jr. <wtogami@gmail.com> wrote:
Anti-DoS Low Hanging Fruit: source IP or subnet connection limits
If you disallow the same IP and/or subnet from establishing too many TCP connections with your node, it becomes more expensive for attackers to use a single host exhaust a target node's resources.  This iptables firewall based example has almost zero drawbacks, but it is too complicated for most people to deploy.  Yes, there is a small chance that you will block legitimate connections, but there are plenty of other nodes for random connections to choose from.  Configurable per source IP and source subnet limits with sane defaults enforced by bitcoind itself would be a big improvement over the current situation where one host address can consume limited resources of many target nodes.

This doesn't remove the risk of a network-wide connection exhaustion attack by a determined attacker, but it at least makes multiple types of attacks a lot more expensive.  This also doesn't do much against the io vulnerability, which would require major redesigns to prevent in Bitcoin.

Want to safely delay the block size limit increase for another year or two?  This patch alone enables that.



On Fri, Aug 16, 2013 at 2:24 AM, Mike Hearn <mike@plan99.net> wrote:
The only other thing I'd like to see there is the start of a new anti-DoS framework. I think once the outline is in place other people will be able to fill it in appropriately. But the current framework has to be left behind.

If I had to choose one thing to evict to make time for that, it'd be the whitepapers. At the moment we still have plenty of headroom in block sizes, even post April. It can probably be safely delayed for a while.


On Fri, Aug 16, 2013 at 2:11 PM, Mike Hearn <mike@plan99.net> wrote:
Cool. Maybe it's time for another development update on the foundation blog?


On Fri, Aug 16, 2013 at 3:00 AM, Gavin Andresen <gavinandresen@gmail.com> wrote:
Mike asked what non-0.9 code I'm working on; the three things on the top of my list are:

1) Smarter fee handling on the client side, instead of hard-coded fees. I was busy today generating scatter-plots and histograms of transaction fees versus priorities to get some insight into what miner policies look like right now.

2) "First double-spend" relaying and alerting, to better support low-value in-person transactions.  Related: 

Have a Snack, Pay with Bitcoins 


3) Work on 2-3 whitepapers on why we need to increase or remove the 1MB block size limit, how we can do it safely, and go through all of the arguments that have been made against it and explain why they're wrong.

--
--
Gavin Andresen




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