# WHATPORT(100)

## NAME

port 100 — Unassigned (historically "newacct") — Unassigned by IANA; `/etc/services` still lists it as newacct and flags it as unauthorized use.

Protocol: TCP  
IANA registry

## DESCRIPTION

IANA marks TCP 100 as Unassigned. Most Unix `/etc/services` files nonetheless carry the line `newacct 100/tcp # [unauthorized use]` — a squatted "new account" service that was never registered, and the comment is IANA's own note that the usage is unsanctioned. So a scanner may label an open 100 "newacct" while no such protocol is defined. Treat the label as historical trivia and fingerprint whatever is actually listening.

## EXPOSURE

**Expose with care.** There is no standard service to reason about here; an open 100 is an unknown listener until you identify it.

## CHECK

```sh
nc -vz TARGET 100
```

## SEE ALSO

- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/100/> · JSON: <https://whatport.net/100.json> · full dataset: <https://whatport.net/ports.json>