12-30-2016
tcp ports are dictated by IANA So if you decide to "secure" port 25, nobody will be able to connect using ftp.
This link has 140 pages, just read a few.
Service Name and Transport Protocol Port Number Registry
My point is: you can break all kinds of services without knowing why. And if someone attacks a random port and there is no service behind it to respond, the attacks fails. So no need to block it. This is why attacks go for a lot of known ports. So known ports may require a minor tweak.
Are you trying to harden your box for a reason? A lot of linux boxes have special apps to help you. What OS and version of it do you have?
uname -a will show that, so please post it.
Edit: It is not uncommon to harden a UNIX and break some applications.
Last edited by jim mcnamara; 12-30-2016 at 09:02 PM..
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LEARN ABOUT HPUX
services
services(4) Kernel Interfaces Manual services(4)
NAME
services - service name data base
DESCRIPTION
The file associates official service names and aliases with the port number and protocol the services use. For each service a single line
should be present with the following information:
<official service name> <port number/protocol name> <aliases>
Port numbers 0 through 1023 are assigned by RFC 1700. This RFC also lists the conventional use of various ports with numbers greater than
1023.
Aliases are other names under which a service is known. Library routines such as can be invoked with a service alias instead of the ser-
vice official name. For example:
In this example, can be invoked with instead of
instead of
Both produce the same results.
Items are separated by any number of blanks (space or tab characters in any combination). The port number and protocol name are considered
a single item. A is used to separate the port and protocol (for example, A character indicates the beginning of a comment. Characters
from the to the end of the line are not interpreted by routines which search the file.
Service names can contain any printable character other than a white space, newline, or comment character. Trailing blanks (spaces or
tabs) are allowed at the end of a line.
Not all services listed in this file are available on HP-UX.
EXAMPLES
AUTHOR
was developed by the University of California, Berkeley.
FILES
SEE ALSO
getservent(3N).
services(4)