With tarpitting enabled, if a sender attempts to issue commands to the mail server before the banner, the connection is dropped:[root@localhost ~]# telnet test.corp.interworx.com 25
Connected to test.corp.interworx.com.
Escape character is ‘^]’.
554 SMTP protocol violation
Connection closed by foreign host.
To enable tarpitting, follow these steps:
- At the command line, use your text editor to view
/etc/tcprules.d/tcp.smtp. It will look similar to the following:
2. At the end of the line beginning with :allow, add the following: