>Date: Thu, 24 Oct 1996 11:06:10 +0200
>From: Dante Profeta <profeta@neomedia.it>
>
>I'm wondering about the behaviour of /dev/tty*
>
>How do they works?
>
>Why there are some ttys permissions with crw-rw-rw (generally owned by
>root, but some others owned by users), and some others with crw-------
>permissions (owned only by users)?

The users with mode 600 TTYs have used 'mesg n' to disable write(1).
See mesg(1).

>What is the 'c' bit? I've no docs about it.

The 'c' indicates that the file is a character device node.

>Are there any security problems about ttys permissions?

Certainly.  Malicious users can use write(1) to send garbage to your
terminal, possibly including control characters that do Interesting
Things.
-- 
Mike Long <mike.long@analog.com>     <URL:http://www.shore.net/~mikel>
VLSI Design Engineer         finger mikel@shore.net for PGP public key
Analog Devices, CPD Division          CCBF225E7D3F7ECB2C8F7ABB15D9BE7B
Norwood, MA 02062 USA       (eq (opinion 'ADI) (opinion 'mike)) -> nil