It is always a good idea to keep your operating system up to date. To keep list traffic manageably, ITSO alerts report only security problems. There are many other kinds of bugs. For this reason, the UWSG recommends downloading and installing your OS's recommended patches at least once a month. Disabling Unneeded Network Services Patches can go only so far.
Some services are intrinsically insecure.
Unfortunately, a slew of insecure and seldom-used services is enabled at installation time. A just-installed Unix box is never secure. The generic Internet daemon, inetd , reads this file when it is first started so it knows which services to provide. You want it to refuse requests for insecure servives. This is the chargen service, used only for testing.