Questions concerning Security Log

[Paul Howarth]

On Thu, 2005-04-07 at 09:14 +0300, Dotan Cohen wrote:
> As I'm still new to linux I like to open things and see what they are
> / do. So I opened the KDE System Logs program, clicked on over to
> Security logs, and found a bunch of these:
> 
> Apr  4 02:15:03 localhost sshd[26567]: Failed password for invalid
> user test from ::ffff:219.238.239.10 port 3429 ssh2

This is a script kiddie trying to crack passwords on your ssh server.

> and these:
> 
> Apr  5 04:47:24 localhost sshd[7287]: reverse mapping checking
> getaddrinfo for h169-210-68-8.adcast.com.tw failed - POSSIBLE BREAKIN
> ATTEMPT!

This is because reverse DNS for 210.68.8.169 (source of one of the
script kiddie attacks) points to the hostname
h169-210-68-8.adcast.com.tw but that name does not resolve. Not terribly
uncommon with incompetent ISPs.

> and many more like it. Is this something to worry about?

Yes it is, but it's nothing personal. Everyone running a ssh server that
isn't firewalled off except for specific IPs is probably getting them. I
know I am.

Suggestions:

1. Disable root logins in ssh (you can still log in as a regular user
and use "su") by putting "PermitRootLogin no" in /etc/ssh/sshd_config.

2. Make sure you use strong passwords for *all* accounts.

3. Consider turning off password authentication altogether and using
certificates instead.

> Chkrootkit
> didn't find anything suspicious, so that makes me feel a little
> better, but as I am unable to start firestarter I am a little nervous.
> 
> By the way, what is the difference between chkrootkit and chkrootkitX?
> They both run in the terminal (I thought that chkrootkitX would open
> up in a gui or something).

Don't know; I've never used chkrootkit.

> Is it unsafe to put a copy of the log on my site and post a link to it
> here? it spans about 1500 lines, so I do not want to email it to the
> list.

Probably fairly safe but not very useful.

Paul.
-- 
Paul Howarth <paul at city-fan.org>