[CentOS] Email dictionary attacks and firewall

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I keep seeing 'Joe Average compromised computer on broadband' being used to do email dictionary attacks on our systems. Seems I always have several domains going through these. One in particular has been in the 'a-' list for weeks with about 20,000 attempts per day from various systems. Yeah, I do have a system which blocks email from these systems for a period of time after 3 bad email address attempts.... throttling...

Anyway, this brought to mind.... Joe Average! Joe Average buys a broadband connection, has someone hook up his computer.. talks to tech support about everything and eventually, an AV subscription dies or something and Joe just doesn't care or doesn't know how to deal with that. Meanwhile Joe's computer gets a virus allowing some baddy to start sending email. Joe notices his computer is getting a little slow.. but it's not bad enough to worry about.

So, this made me start wondering about how to do something that makes Joe's computer so slow that he finally gives up and calls in tech support to fix the damned thing.

I wonder if there is a way that a firewall rule could be written, that would let a trickle of the connection from Joe through, so as his dictionary attack gets backed up with a huge number of connections which are trickling through at such a slow rate, with maybe just enough delay built in to make it keep trying.... Basically making Joe's compromised computer useless.. and maybe he'd at least turn it off if it didn't lock up all by itself....

It is so very sad that some providers don't monitor their own people. I see where comcast has now slid down to number 8 after holding the number one spot as the biggest spammer network for a very long time. Good for them! It seems the undisputed king of this world now is verizonbusiness.com.... bad bad very bad....

Sorry.. yeah.. a bit off topic......

John Hinton
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