How to be more or less aware of the security of a linux server?

Question

Information Security

There is a server running a self-written HTTP server and sshd. No more apache/php, just two daemons - port 22 and 80. What do you need to know about, what to watch out for, except for holes in your demon? Behind vulnerabilities in the current kernel version? Behind the vulnerabilities in the sshd daemon? In which lists to look for your kernel version in order to know about the current holes in it? Similar question on sshd. What is the best way to ensure that what happened afterwards is understood? Have a complete sniff of its traffic independent of the guarded server?

Answer 1

You need to specify the distribution kit, bldzhad, in such matters.
www.ubuntu.com/usn
https://www.debian.org/security/
https://access.redhat.com/security/