~$ cat /etc/services
# Network services, Internet style
#
# Note that it is presently the policy of IANA to assign a single well-known
# port number for both TCP and UDP; hence, officially ports have two entries
# even if the protocol doesn't support UDP operations.
#
# Updated from https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml .
#
# New ports will be added on request if they have been officially assigned
# by IANA and used in the real-world or are needed by a debian package.
# If you need a huge list of used numbers please install the nmap package.
tcpmux 1/tcp # TCP port service multiplexer
echo 7/tcp
echo 7/udp
discard 9/tcp sink null
discard 9/udp sink null
systat 11/tcp users
daytime 13/tcp
daytime 13/udp
netstat 15/tcp
qotd 17/tcp quote
chargen 19/tcp ttytst source
chargen 19/udp ttytst source
ftp-data 20/tcp
ftp 21/tcp
fsp 21/udp fspd
ssh 22/tcp # SSH Remote Login Protocol
telnet 23/tcp
smtp 25/tcp mail
time 37/tcp timserver
time 37/udp timserver
whois 43/tcp nicname
tacacs 49/tcp # Login Host Protocol (TACACS)
tacacs 49/udp
domain 53/tcp # Domain Name Server
domain 53/udp
bootps 67/udp
bootpc 68/udp
tftp 69/udp
gopher 70/tcp # Internet Gopher
finger 79/tcp
http 80/tcp www # WorldWideWeb HTTP
To co prawda jest z Linuxa, ale porty są uniwersalne. Jest oczywiście tylko początek pliku. W Windowsie też może być gdzieś taki plik.
23 (telnet) jest bardzo podejrzany - czasami występuje w jakiś urządzeniach sieciowych do sterowania. Komputery praktycznie tego portu nie słuchają. 79 (finger) to też już od dawna zabytek.
