I’ve had a postfix(SASL) mail server running well for a long time with no problems. However recently I’ve installed vsftp to allow users to login and download files.
I created a linux user with a generic username/password which I thought didn’t matter as I had disabled ssh login and wasn’t too concerned if anyone had logged into the ftp account (read-only access). However what I hadn’t realised was that several spammers have brute forced entry (logging into SASL) and sending emails.
Is there any way to disable the linux user for mail but keep the credentials the same for vsftp?
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Answer
I ended up removing the linux user and adding the user as a user for vsftp. This then still allowed the username/password to work and disabled the intruder from using the server as a spam server. Issue resolved :).