Cybersecurity Triage
Read-onlyShow Publicly Bound Listeners
You need to filter listening sockets down to services bound on all interfaces or IPv6 wildcard addresses.
Command
ss -ltnp | awk 'NR==1 || $4 ~ /^(0[.]0[.]0[.]0|[[]::[]]|[*]):/'Before you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not ignore IPv6, container ports, or cloud firewalls on real hosts; this is the host-level socket view.
Expected output
The ss header plus listeners bound to public wildcard addresses.
System impact
Read-only. Nothing changes. awk filters socket output by bind address.
Recovery / rollback: no state is changed.
When to use it
Use when you need a quick public-exposure worklist before comparing against firewall policy.
When not to use it
Do not ignore IPv6, container ports, or cloud firewalls on real hosts; this is the host-level socket view.
Watch this command run
Command transcript
This sanitized transcript shows the commands and output shape without exposing host details.
$ ss -ltnp
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=801,fd=3))
LISTEN 0 511 0.0.0.0:80 0.0.0.0:* users:(("nginx",pid=1907,fd=6))
LISTEN 0 511 0.0.0.0:443 0.0.0.0:* users:(("nginx",pid=1907,fd=7))
LISTEN 0 128 localhost:5432 0.0.0.0:* users:(("postgres",pid=2011,fd=7))
LISTEN 0 128 localhost:6379 0.0.0.0:* users:(("redis-server",pid=2112,fd=6))
LISTEN 0 64 0.0.0.0:9000 0.0.0.0:* users:(("node",pid=2219,fd=18))$ ss -ltnp | awk 'NR==1 || $4 ~ /^(0[.]0[.]0[.]0|[[]::[]]|[*]):/'
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=801,fd=3))
LISTEN 0 511 0.0.0.0:80 0.0.0.0:* users:(("nginx",pid=1907,fd=6))
LISTEN 0 511 0.0.0.0:443 0.0.0.0:* users:(("nginx",pid=1907,fd=7))
LISTEN 0 64 0.0.0.0:9000 0.0.0.0:* users:(("node",pid=2219,fd=18))View commands shown
These are the commands shown in the sanitized transcript.
Commands shown
ss -ltnpss -ltnp | awk 'NR==1 || $4 ~ /^(0[.]0[.]0[.]0|[[]::[]]|[*]):/'
next steps
Related commands
Show Local-Only Database Listeners
The database was listening, but only on localhost.
ss -ltnp | awk '$4 ~ /^127[.]0[.]0[.]1:(5432|3306|6379)$/ {print}'
Find Public Listeners Not Allowed by UFW
The process was public, but the firewall did not mention it.
comm -13 <(ufw status numbered | awk '/ALLOW/ {print}' | grep -Eo '[0-9]+/(tcp|udp)' | cut -d/ -f1 | sort -u) <(ss -ltnp | awk '$4 ~ /^(0[.]0[.]0[.]0|[[]::[]]|[*]):/ {n=split($4,a,":"); print a[n]}' | sort -u)
Check Whether SSH Is Publicly Bound
SSH can be locked down by source and still bind publicly.
ss -ltnp | awk '$4 ~ /:22$/ && $4 !~ /^127[.]/ {print}'
Check Whether Databases Listen Publicly
The fastest database security check is the listening address.
ss -ltnp | awk '$4 ~ /:(5432|3306)$/ {print}'
Find Allowed Ports with No Listener
An open firewall rule can outlive the service it was created for.
comm -23 <(ufw status numbered | awk '/ALLOW/ {print}' | grep -Eo '[0-9]+/(tcp|udp)' | cut -d/ -f1 | sort -u) <(ss -ltnp | awk '/LISTEN/ {n=split($4,a,":"); print a[n]}' | sort -u)
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Useful for
- LPIC-1 style command-line practice
- LFCS style performance tasks
- Linux+ style troubleshooting review
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.