Sabri, A clever idea to be sure, but it seems open to abuse. What stops someone from forging a tcp syn from every /24 on the Internet, causing you to blackhole your access to everywhere? -mel
On Apr 29, 2020, at 2:24 PM, Sabri Berisha <sabri@cluecentral.net> wrote:
----- On Apr 29, 2020, at 9:08 AM, Stephen Satchell list@satchell.net wrote:
Hi,
That said, I use TCPWRAPPER to limit access to SSH to specific IP addresses. I process my LogWatch messages manually. I pull the fire alarm for showshoe probes, and excessive number of probes (over 30 in a 24-hour period). No registered abuse@ address in the WHOIS? The offending netblock goes into my edge router ACL, because I have learned that ne'er-do-wells without working abuse@ usually have other bad habits.
I have a very simple method to deal with that: a server with no other purpose than to blackhole portscanning culprits. Send so much as a tcp syn to port 22 and your entire /24 goes to null0 for a month. I have a few exceptions for entities that I know are responsive to abuse@, but that's it.
Highly effective.
Thanks,
Sabri