On 05.09.21 05:00, Deepak Garg wrote: > Need two help, we are using OpenSSH 7.x on a Windows Server 2019 for SFTP > connection from public IPs. > We are facing an issue that every few minutes (10-15), connection from > outside stop working and error is "Connection Refused". > We didn't find anything in the logs and logs don't make any entry for such, > to resolve the issue for now we have enabled a task in Windows to restart > the OPenssh service every 10 minutes and now its working. > > Any suggestion, how we can troubleshoot? I'm not familiar with the Win part (in particular, how it affects the possibilities to make the log more verbose for debugging), but on the sshd_config side, you might want to experiment with: -- lowering LoginGraceTime and MaxAuthTries (to clean out failing login attempts, read, script kiddies, faster) -- varying MaxSessions (less for "bad guys", more for legit users, maybe using a Match statement to tell the two apart) -- raising MaxStartups (temporarily, just to see if unauthenticated connections *are* the root cause and it takes longer until failure) -- if your legit users use keypair auth, try disabling password auth altogether Getting current *counts* of unauthenticated vs. proven-legit connections would be quite valuable, I think ... Regards, -- Jochen Bern Systemingenieur Binect GmbH
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