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Cybersecurity Triage

Read-only, sensitive output

Summarize SSH Authorized Key Types

You need to count SSH key algorithms used in authorized_keys files.

Command

find /home -path '*/.ssh/authorized_keys' -exec awk '{print $1}' {} + 2>/dev/null | sort | uniq -c | sort -nr

Before you run this

System impact: Read-only. Output may expose users, paths, tokens, keys, IPs, process arguments, or log details.

When not to use it: Do not delete RSA keys solely because they appear here; confirm policy, fingerprint, owner, and compatibility first.

Expected output

A count-sorted list of authorized SSH key types.

System impact

Read-only, sensitive output. Nothing changes. The command reads authorized_keys files and counts the first field, which is the key type.

Recovery / rollback: no state is changed.

When to use it

Use during SSH access reviews when you need to spot legacy key types before planning cleanup.

When not to use it

Do not delete RSA keys solely because they appear here; confirm policy, fingerprint, owner, and compatibility first.

next steps

Related commands

Cybersecurity Triage Sensitive output

Inventory SSH authorized_keys

authorized_keys files are the practical list of who can use key-based SSH.

find /home -path '*/.ssh/authorized_keys' -exec awk '{print FILENAME, $1, $NF}' {} + 2>/dev/null

Cybersecurity Triage Sensitive output

Find SSH Key Users with sudo

The highest-priority access review starts where SSH keys and sudo overlap.

comm -12 <(find /home -path '*/.ssh/authorized_keys' -printf '%h\n' 2>/dev/null | awk -F/ '{print $(NF-1)}' | sort) <(awk -F: '$1=="sudo" {gsub(",","\n",$4); print $4}' /etc/group | sort)

Cybersecurity Triage Sensitive output

Find SSH Keys for nologin Users

A nologin shell does not automatically mean SSH keys are irrelevant.

comm -12 <(awk -F: '$7 !~ /(bash|sh|zsh)$/ {print $1}' /etc/passwd | sort) <(find /home -path '*/.ssh/authorized_keys' -printf '%h\n' 2>/dev/null | awk -F/ '{print $(NF-1)}' | sort)

Cybersecurity Triage Sensitive output

Count authorized_keys by User

authorized_keys is the practical SSH access list.

find /home -path '*/.ssh/authorized_keys' -exec sh -c 'for f do user=$(basename "$(dirname "$(dirname "$f")")"); keys=$(grep -vc "^[[:space:]]*#" "$f"); printf "%s %s %s\n" "$user" "$keys" "$f"; done' sh {} + 2>/dev/null | sort

Cybersecurity Triage Sensitive output

Find Loose authorized_keys Modes

SSH key access files should not be looser than intended.

find /home -path '*/.ssh/authorized_keys' -printf '%m %p\n' 2>/dev/null | awk '$1 > 600'

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.

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