What it is
Forward/reverse proxy ports such as Squid.
Why it is risky
Left as an open proxy, third parties can relay traffic through your IP (spam, attack laundering).
What to do
Restrict users/ranges with an access ACL and make sure it is not an open relay.
Is it listening on your server?
Linux
ss -ltnp 'sport = :3128'Track these versions on your own servers
InfraGuard collects installed software versions from every server and flags the ones with known vulnerabilities. Self-hosted — nothing leaves your network.