Snort IDS installed.

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One way to make your network unattractive to spammers is to make setting up new accounts more expensive for the abuser- either through collecting AUP violation fees, or through high setup fees. Of course, this is difficult with the real black-hats, as they usually pay with fraudulently obtained credit cards. It works ok for the 'grey' spammers- those who mail people who 'opted-in' when they bought something, and now get tangentially related offers.

Another way to do it is to be more proactive about disconnecting abusive customers. See, most of the time, one can expect 4-24 hours between when the abuse is reported and when the provider does something about it- and in my experience, it takes quite a lot of abuse to get a complaint- sometimes the abuse has been going on for a week or more before it hits someone with the spare time and the knowledge to complain.

So my thought is this: why not run an IDS system, but instead of alerting on the constant stream of abuse coming in from the Internet, alert on abuse going out from your customers? you could even then automatically kill the ports belonging to obviously compromised or abusive hosts.

So that's what I did tonight. I setup a VPS on my new server, set my bridge to not remember MAC addresses (that is, I turned it into a hub) and installed snort on that VPS. Right now, it's pretty much just using the default rules and scanning all traffic, incoming and outgoing. Next, I need to set up some good e-mail rules (I want to allow people to run secondary MX servers, but I want to prohibit mailing lists beyond a certain size without my prior approval... I've not quite figured out how to do that.)

I figure if I'm going to be watching you, I should give you something back- so I have decided to give you access to see the snort alerts about people from the Internet trying to attack you. If you are on lion and interested, let me know via email.

I've got a shell script parsing the output, and putting it in a file for each user to watch, if they like. If it encounters an attack coming from one of my e-mail addresses, it e-mails me, meaning a worst-case response of around 8 hours. That's not a great response time if you count from when someone files an abuse report, but if you count from when the abuse starts (and that is what is happening) 8 hours isn't bad at all.

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