example:  knock myserver.example.com 123:tcp 456:udp 789:tcp                                                                                                    admin@i-080ac908debd2d3d7:~$ knock -v 127.0.0.1 80:tcp 1                        hitting tcp 127.0.0.1:80                                                        hitting tcp 127.0.0.1:1                                                         admin@i-080ac908debd2d3d7:~$ knock -v 127.0.0.1 80:tcp                          hitting tcp 127.0.0.1:80                                                        admin@i-080ac908debd2d3d7:~$ curl -D - -v localhost                             *   Trying 127.0.0.1:80...                                                      * connect to 127.0.0.1 port 80 failed: Connection refused                       * Failed to connect to localhost port 80: Connection refused                    * Closing connection 0                                                          curl: (7) Failed to connect to localhost port 80: Connection refused            admin@i-080ac908debd2d3d7:~$ nc -vv 12                                          

     24 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 netns         25 root      20   0       0      0      0 S   0.0   0.0   0:00.12 kauditd       26 root      20   0       0      0      0 S   0.0   0.0   0:00.00 khungtask     27 root      20   0       0      0      0 S   0.0   0.0   0:00.00 oom_reape     28 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 writeback     29 root      20   0       0      0      0 S   0.0   0.0   0:00.00 kcompactd     30 root      25   5       0      0      0 S   0.0   0.0   0:00.00 ksmd          49 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kintegrit     50 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kblockd       51 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 blkcg_pun     52 root      20   0       0      0      0 I   0.0   0.0   0:00.03 kworker/1     53 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kworker/0     54 root      20   0       0      0      0 S   0.0   0.0   0:00.00 kswapd0       55 root       0 -20       0      0      0 I   0.0   0.0   0:00.00 kthrotld admin@i-0bc8be230e1a6d230:~$ lso                                                

114  23   52   593  710        dynamic_debug  loadavg       swaps               115  235  53   595  73         execdomains    locks         sys                 12   24   54   596  78         fb             meminfo       sysrq-trigger       13   25   55   6    8          filesystems    misc          sysvipc             133  26   56   60   889        fs             modules       thread-self         134  27   565  61   9          interrupts     mounts        timer_list          14   28   566  614  acpi       iomem          mtrr          tty                 15   29   57   62   buddyinfo  ioports        net           uptime              16   3    572  63   bus        irq            pagetypeinfo  version             17   30   575  682  cgroups    kallsyms       partitions    vmallocinfo         18   31   58   685  cmdline    kcore          pressure      vmstat              19   311  582  690  consoles   key-users      sched_debug   zoneinfo            195  395  583  693  cpuinfo    keys           schedstat                         2    4    586  694  crypto     kmsg           self                              admin@i-09f337b8d012c50bc:~$ ls /proc/                                          

admin@i-0102423b4d32663a7:~$ curl 127.0.0.1:5000                                Unauthorizedadmin@i-0102423b4d32663a7:~$                                        admin@i-0102423b4d32663a7:~$                                                    admin@i-0102423b4d32663a7:~$ ls                                                 agent  webserver.py                                                             admin@i-0102423b4d32663a7:~$ less webserver.py                                  webserver.py: Permission denied                                                 admin@i-0102423b4d32663a7:~$ ll                                                 bash: ll: command not found                                                     admin@i-0102423b4d32663a7:~$ cat webserver.py                                   cat: webserver.py: Permission denied                                            admin@i-0102423b4d32663a7:~$ cd agent/                                          admin@i-0102423b4d32663a7:~/agent$ ls                                           check.sh  sadagent  sadagent.txt                                                admin@i-0102423b4d32663a7:~/agent$ ls