Information
The recommendation is to change both the default sendmail greeting and HELP output to not display the sendmail version.
The sendmail deamon has a history of security vulnerabilities. The recommendation is to change the default sendmail settings that display the sendmail version and other related information. Sendmail version information can be used by an attacker for fingerprinting purposes.
Solution
Create a backup copy of /etc/mail/sendmail.cf :
cp -p /etc/mail/sendmail.cf /etc/mail/sendmail.cf.pre_cis
Edit:
vi /etc/mail/sendmail.cf
Replace:
O SmtpGreetingMessage=$j Sendmail $b
With:
O SmtpGreetingMessage=mailerready
- Ensure Sendmail helpfile exists
test -e /etc/mail/helpfile || touch /etc/mail/helpfile