Check open ports

Are there any open ports that shouldn’t be open? Check with:

sudo netstat -tupl

Results in something like:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address    Foreign Address  State    PID/Program name
tcp        0      0 localhost:mysql  *:*              LISTEN  5077/mysqld
tcp        0      0 localhost:ipp    *:*              LISTEN  5001/cupsd
udp        0      0 *:32768          *:*                      5324/avahi-daemon:
udp        0      0 *:bootpc         *:*                      5875/dhclient
udp        0      0 *:mdns           *:*                      5324/avahi-daemon: 

Kill the process that is using the port

kill (PID here)

List open files:

lsof -i

where the -i makes it list internet files.